From dae1b15e92f95c6750c8014d8c90a6e169980bdd Mon Sep 17 00:00:00 2001
From: Chengcheng Zhang <943420582@qq.com>
Date: Fri, 27 Jul 2018 14:44:50 +0800
Subject: [PATCH] add sm2 (#1193)

* add sm2

* fix import
---
 crypto/sm2/cert_pool.go |  229 +++++
 crypto/sm2/p256.go      | 1056 ++++++++++++++++++++
 crypto/sm2/pkcs1.go     |  132 +++
 crypto/sm2/pkcs8.go     |  488 +++++++++
 crypto/sm2/sm2.go       |  524 ++++++++++
 crypto/sm2/sm2_test.go  |  219 ++++
 crypto/sm2/verify.go    |  568 +++++++++++
 crypto/sm2/x509.go      | 2527 +++++++++++++++++++++++++++++++++++++++++++++++
 crypto/sm3/sm3_test.go  |    1 +
 9 files changed, 5744 insertions(+)
 create mode 100644 crypto/sm2/cert_pool.go
 create mode 100644 crypto/sm2/p256.go
 create mode 100644 crypto/sm2/pkcs1.go
 create mode 100644 crypto/sm2/pkcs8.go
 create mode 100644 crypto/sm2/sm2.go
 create mode 100644 crypto/sm2/sm2_test.go
 create mode 100644 crypto/sm2/verify.go
 create mode 100644 crypto/sm2/x509.go

diff --git a/crypto/sm2/cert_pool.go b/crypto/sm2/cert_pool.go
new file mode 100644
index 00000000..8230c4d1
--- /dev/null
+++ b/crypto/sm2/cert_pool.go
@@ -0,0 +1,229 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sm2
+
+import (
+	"encoding/pem"
+	"errors"
+	"io/ioutil"
+	"os"
+	"runtime"
+	"sync"
+)
+
+// Possible certificate files; stop after finding one.
+var certFiles = []string{
+	"/etc/ssl/certs/ca-certificates.crt",                // Debian/Ubuntu/Gentoo etc.
+	"/etc/pki/tls/certs/ca-bundle.crt",                  // Fedora/RHEL 6
+	"/etc/ssl/ca-bundle.pem",                            // OpenSUSE
+	"/etc/pki/tls/cacert.pem",                           // OpenELEC
+	"/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem", // CentOS/RHEL 7
+}
+
+// CertPool is a set of certificates.
+type CertPool struct {
+	bySubjectKeyId map[string][]int
+	byName         map[string][]int
+	certs          []*Certificate
+}
+
+// NewCertPool returns a new, empty CertPool.
+func NewCertPool() *CertPool {
+	return &CertPool{
+		bySubjectKeyId: make(map[string][]int),
+		byName:         make(map[string][]int),
+	}
+}
+
+// Possible directories with certificate files; stop after successfully
+// reading at least one file from a directory.
+var certDirectories = []string{
+	"/etc/ssl/certs",               // SLES10/SLES11, https://golang.org/issue/12139
+	"/system/etc/security/cacerts", // Android
+}
+
+var (
+	once           sync.Once
+	systemRoots    *CertPool
+	systemRootsErr error
+)
+
+func systemRootsPool() *CertPool {
+	once.Do(initSystemRoots)
+	return systemRoots
+}
+
+func initSystemRoots() {
+	systemRoots, systemRootsErr = loadSystemRoots()
+}
+
+func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	return nil, nil
+}
+
+func loadSystemRoots() (*CertPool, error) {
+	roots := NewCertPool()
+	var firstErr error
+	for _, file := range certFiles {
+		data, err := ioutil.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+		if firstErr == nil && !os.IsNotExist(err) {
+			firstErr = err
+		}
+	}
+
+	for _, directory := range certDirectories {
+		fis, err := ioutil.ReadDir(directory)
+		if err != nil {
+			if firstErr == nil && !os.IsNotExist(err) {
+				firstErr = err
+			}
+			continue
+		}
+		rootsAdded := false
+		for _, fi := range fis {
+			data, err := ioutil.ReadFile(directory + "/" + fi.Name())
+			if err == nil && roots.AppendCertsFromPEM(data) {
+				rootsAdded = true
+			}
+		}
+		if rootsAdded {
+			return roots, nil
+		}
+	}
+
+	return nil, firstErr
+}
+
+// SystemCertPool returns a copy of the system cert pool.
+//
+// Any mutations to the returned pool are not written to disk and do
+// not affect any other pool.
+func SystemCertPool() (*CertPool, error) {
+	if runtime.GOOS == "windows" {
+		// Issue 16736, 18609:
+		return nil, errors.New("crypto/x509: system root pool is not available on Windows")
+	}
+
+	return loadSystemRoots()
+}
+
+// findVerifiedParents attempts to find certificates in s which have signed the
+// given certificate. If any candidates were rejected then errCert will be set
+// to one of them, arbitrarily, and err will contain the reason that it was
+// rejected.
+func (s *CertPool) findVerifiedParents(cert *Certificate) (parents []int, errCert *Certificate, err error) {
+	if s == nil {
+		return
+	}
+	var candidates []int
+
+	if len(cert.AuthorityKeyId) > 0 {
+		candidates = s.bySubjectKeyId[string(cert.AuthorityKeyId)]
+	}
+	if len(candidates) == 0 {
+		candidates = s.byName[string(cert.RawIssuer)]
+	}
+
+	for _, c := range candidates {
+		if err = cert.CheckSignatureFrom(s.certs[c]); err == nil {
+			parents = append(parents, c)
+		} else {
+			errCert = s.certs[c]
+		}
+	}
+
+	return
+}
+
+func (s *CertPool) contains(cert *Certificate) bool {
+	if s == nil {
+		return false
+	}
+
+	candidates := s.byName[string(cert.RawSubject)]
+	for _, c := range candidates {
+		if s.certs[c].Equal(cert) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// AddCert adds a certificate to a pool.
+func (s *CertPool) AddCert(cert *Certificate) {
+	if cert == nil {
+		panic("adding nil Certificate to CertPool")
+	}
+
+	// Check that the certificate isn't being added twice.
+	if s.contains(cert) {
+		return
+	}
+
+	n := len(s.certs)
+	s.certs = append(s.certs, cert)
+
+	if len(cert.SubjectKeyId) > 0 {
+		keyId := string(cert.SubjectKeyId)
+		s.bySubjectKeyId[keyId] = append(s.bySubjectKeyId[keyId], n)
+	}
+	name := string(cert.RawSubject)
+	s.byName[name] = append(s.byName[name], n)
+}
+
+// AppendCertsFromPEM attempts to parse a series of PEM encoded certificates.
+// It appends any certificates found to s and reports whether any certificates
+// were successfully parsed.
+//
+// On many Linux systems, /etc/ssl/cert.pem will contain the system wide set
+// of root CAs in a format suitable for this function.
+func (s *CertPool) AppendCertsFromPEM(pemCerts []byte) (ok bool) {
+	for len(pemCerts) > 0 {
+		var block *pem.Block
+		block, pemCerts = pem.Decode(pemCerts)
+		if block == nil {
+			break
+		}
+		if block.Type != "CERTIFICATE" || len(block.Headers) != 0 {
+			continue
+		}
+
+		cert, err := ParseCertificate(block.Bytes)
+		if err != nil {
+			continue
+		}
+
+		s.AddCert(cert)
+		ok = true
+	}
+
+	return
+}
+
+// Subjects returns a list of the DER-encoded subjects of
+// all of the certificates in the pool.
+func (s *CertPool) Subjects() [][]byte {
+	res := make([][]byte, len(s.certs))
+	for i, c := range s.certs {
+		res[i] = c.RawSubject
+	}
+	return res
+}
diff --git a/crypto/sm2/p256.go b/crypto/sm2/p256.go
new file mode 100644
index 00000000..a7293238
--- /dev/null
+++ b/crypto/sm2/p256.go
@@ -0,0 +1,1056 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sm2
+
+import (
+	"crypto/elliptic"
+	"math/big"
+	"sync"
+)
+
+/** 学习标准库p256的优化方法实现sm2的快速版本
+ * 标准库的p256的代码实现有些晦涩难懂，当然sm2的同样如此，有兴趣的大家可以研究研究，最后神兽压阵。。。
+ *
+ * ━━━━━━animal━━━━━━
+ * 　　　┏┓　　　┏┓
+ * 　　┏┛┻━━━┛┻┓
+ * 　　┃　　　　　　　┃
+ * 　　┃　　　━　　　┃
+ * 　　┃　┳┛　┗┳　┃
+ * 　　┃　　　　　　　┃
+ * 　　┃　　　┻　　　┃
+ * 　　┃　　　　　　　┃
+ * 　　┗━┓　　　┏━┛
+ * 　　　┃　　　┃
+ *　　 　┃　　　┃
+ *　　　 ┃　　　┗━━━┓
+ *	   　┃　　　　　┣┓
+ *   　　┃　　　　　┏┛
+ *　　 　┗┓┓┏━┳┓┏┛
+ *　　　　┃┫┫ ┃┫┫
+ *　　　　┗┻┛ ┗┻┛
+ *
+ * ━━━━━Kawaii ━━━━━━
+ */
+
+type sm2P256Curve struct {
+	RInverse *big.Int
+	*elliptic.CurveParams
+	a, b, gx, gy sm2P256FieldElement
+}
+
+var initonce sync.Once
+var sm2P256 sm2P256Curve
+
+type sm2P256FieldElement [9]uint32
+type sm2P256LargeFieldElement [17]uint64
+
+const (
+	bottom28Bits = 0xFFFFFFF
+	bottom29Bits = 0x1FFFFFFF
+)
+
+func initP256Sm2() {
+	sm2P256.CurveParams = &elliptic.CurveParams{Name: "SM2-P-256"} // sm2
+	A, _ := new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFC", 16)
+	//SM2椭	椭 圆 曲 线 公 钥 密 码 算 法 推 荐 曲 线 参 数
+	sm2P256.P, _ = new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF", 16)
+	sm2P256.N, _ = new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123", 16)
+	sm2P256.B, _ = new(big.Int).SetString("28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93", 16)
+	sm2P256.Gx, _ = new(big.Int).SetString("32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7", 16)
+	sm2P256.Gy, _ = new(big.Int).SetString("BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0", 16)
+	sm2P256.RInverse, _ = new(big.Int).SetString("7ffffffd80000002fffffffe000000017ffffffe800000037ffffffc80000002", 16)
+	sm2P256.BitSize = 256
+	sm2P256FromBig(&sm2P256.a, A)
+	sm2P256FromBig(&sm2P256.gx, sm2P256.Gx)
+	sm2P256FromBig(&sm2P256.gy, sm2P256.Gy)
+	sm2P256FromBig(&sm2P256.b, sm2P256.B)
+}
+
+func P256Sm2() elliptic.Curve {
+	initonce.Do(initP256Sm2)
+	return sm2P256
+}
+
+func (curve sm2P256Curve) Params() *elliptic.CurveParams {
+	return sm2P256.CurveParams
+}
+
+// y^2 = x^3 + ax + b
+func (curve sm2P256Curve) IsOnCurve(X, Y *big.Int) bool {
+	var a, x, y, y2, x3 sm2P256FieldElement
+
+	sm2P256FromBig(&x, X)
+	sm2P256FromBig(&y, Y)
+
+	sm2P256Square(&x3, &x)       // x3 = x ^ 2
+	sm2P256Mul(&x3, &x3, &x)     // x3 = x ^ 2 * x
+	sm2P256Mul(&a, &curve.a, &x) // a = a * x
+	sm2P256Add(&x3, &x3, &a)
+	sm2P256Add(&x3, &x3, &curve.b)
+
+	sm2P256Square(&y2, &y) // y2 = y ^ 2
+	return sm2P256ToBig(&x3).Cmp(sm2P256ToBig(&y2)) == 0
+}
+
+func zForAffine(x, y *big.Int) *big.Int {
+	z := new(big.Int)
+	if x.Sign() != 0 || y.Sign() != 0 {
+		z.SetInt64(1)
+	}
+	return z
+}
+
+func (curve sm2P256Curve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int) {
+	var X1, Y1, Z1, X2, Y2, Z2, X3, Y3, Z3 sm2P256FieldElement
+
+	z1 := zForAffine(x1, y1)
+	z2 := zForAffine(x2, y2)
+	sm2P256FromBig(&X1, x1)
+	sm2P256FromBig(&Y1, y1)
+	sm2P256FromBig(&Z1, z1)
+	sm2P256FromBig(&X2, x2)
+	sm2P256FromBig(&Y2, y2)
+	sm2P256FromBig(&Z2, z2)
+	sm2P256PointAdd(&X1, &Y1, &Z1, &X2, &Y2, &Z2, &X3, &Y3, &Z3)
+	return sm2P256ToAffine(&X3, &Y3, &Z3)
+}
+
+func (curve sm2P256Curve) Double(x1, y1 *big.Int) (*big.Int, *big.Int) {
+	var X1, Y1, Z1 sm2P256FieldElement
+
+	z1 := zForAffine(x1, y1)
+	sm2P256FromBig(&X1, x1)
+	sm2P256FromBig(&Y1, y1)
+	sm2P256FromBig(&Z1, z1)
+	sm2P256PointDouble(&X1, &Y1, &Z1, &X1, &Y1, &Z1)
+	return sm2P256ToAffine(&X1, &Y1, &Z1)
+}
+
+func (curve sm2P256Curve) ScalarMult(x1, y1 *big.Int, k []byte) (*big.Int, *big.Int) {
+	var scalarReversed [32]byte
+	var X, Y, Z, X1, Y1 sm2P256FieldElement
+
+	sm2P256FromBig(&X1, x1)
+	sm2P256FromBig(&Y1, y1)
+	sm2P256GetScalar(&scalarReversed, k)
+	sm2P256ScalarMult(&X, &Y, &Z, &X1, &Y1, &scalarReversed)
+	return sm2P256ToAffine(&X, &Y, &Z)
+}
+
+func (curve sm2P256Curve) ScalarBaseMult(k []byte) (*big.Int, *big.Int) {
+	var scalarReversed [32]byte
+	var X, Y, Z sm2P256FieldElement
+
+	sm2P256GetScalar(&scalarReversed, k)
+	sm2P256ScalarBaseMult(&X, &Y, &Z, &scalarReversed)
+	return sm2P256ToAffine(&X, &Y, &Z)
+}
+
+var sm2P256Precomputed = [9 * 2 * 15 * 2]uint32{
+	0x830053d, 0x328990f, 0x6c04fe1, 0xc0f72e5, 0x1e19f3c, 0x666b093, 0x175a87b, 0xec38276, 0x222cf4b,
+	0x185a1bba, 0x354e593, 0x1295fac1, 0xf2bc469, 0x47c60fa, 0xc19b8a9, 0xf63533e, 0x903ae6b, 0xc79acba,
+	0x15b061a4, 0x33e020b, 0xdffb34b, 0xfcf2c8, 0x16582e08, 0x262f203, 0xfb34381, 0xa55452, 0x604f0ff,
+	0x41f1f90, 0xd64ced2, 0xee377bf, 0x75f05f0, 0x189467ae, 0xe2244e, 0x1e7700e8, 0x3fbc464, 0x9612d2e,
+	0x1341b3b8, 0xee84e23, 0x1edfa5b4, 0x14e6030, 0x19e87be9, 0x92f533c, 0x1665d96c, 0x226653e, 0xa238d3e,
+	0xf5c62c, 0x95bb7a, 0x1f0e5a41, 0x28789c3, 0x1f251d23, 0x8726609, 0xe918910, 0x8096848, 0xf63d028,
+	0x152296a1, 0x9f561a8, 0x14d376fb, 0x898788a, 0x61a95fb, 0xa59466d, 0x159a003d, 0x1ad1698, 0x93cca08,
+	0x1b314662, 0x706e006, 0x11ce1e30, 0x97b710, 0x172fbc0d, 0x8f50158, 0x11c7ffe7, 0xd182cce, 0xc6ad9e8,
+	0x12ea31b2, 0xc4e4f38, 0x175b0d96, 0xec06337, 0x75a9c12, 0xb001fdf, 0x93e82f5, 0x34607de, 0xb8035ed,
+	0x17f97924, 0x75cf9e6, 0xdceaedd, 0x2529924, 0x1a10c5ff, 0xb1a54dc, 0x19464d8, 0x2d1997, 0xde6a110,
+	0x1e276ee5, 0x95c510c, 0x1aca7c7a, 0xfe48aca, 0x121ad4d9, 0xe4132c6, 0x8239b9d, 0x40ea9cd, 0x816c7b,
+	0x632d7a4, 0xa679813, 0x5911fcf, 0x82b0f7c, 0x57b0ad5, 0xbef65, 0xd541365, 0x7f9921f, 0xc62e7a,
+	0x3f4b32d, 0x58e50e1, 0x6427aed, 0xdcdda67, 0xe8c2d3e, 0x6aa54a4, 0x18df4c35, 0x49a6a8e, 0x3cd3d0c,
+	0xd7adf2, 0xcbca97, 0x1bda5f2d, 0x3258579, 0x606b1e6, 0x6fc1b5b, 0x1ac27317, 0x503ca16, 0xa677435,
+	0x57bc73, 0x3992a42, 0xbab987b, 0xfab25eb, 0x128912a4, 0x90a1dc4, 0x1402d591, 0x9ffbcfc, 0xaa48856,
+	0x7a7c2dc, 0xcefd08a, 0x1b29bda6, 0xa785641, 0x16462d8c, 0x76241b7, 0x79b6c3b, 0x204ae18, 0xf41212b,
+	0x1f567a4d, 0xd6ce6db, 0xedf1784, 0x111df34, 0x85d7955, 0x55fc189, 0x1b7ae265, 0xf9281ac, 0xded7740,
+	0xf19468b, 0x83763bb, 0x8ff7234, 0x3da7df8, 0x9590ac3, 0xdc96f2a, 0x16e44896, 0x7931009, 0x99d5acc,
+	0x10f7b842, 0xaef5e84, 0xc0310d7, 0xdebac2c, 0x2a7b137, 0x4342344, 0x19633649, 0x3a10624, 0x4b4cb56,
+	0x1d809c59, 0xac007f, 0x1f0f4bcd, 0xa1ab06e, 0xc5042cf, 0x82c0c77, 0x76c7563, 0x22c30f3, 0x3bf1568,
+	0x7a895be, 0xfcca554, 0x12e90e4c, 0x7b4ab5f, 0x13aeb76b, 0x5887e2c, 0x1d7fe1e3, 0x908c8e3, 0x95800ee,
+	0xb36bd54, 0xf08905d, 0x4e73ae8, 0xf5a7e48, 0xa67cb0, 0x50e1067, 0x1b944a0a, 0xf29c83a, 0xb23cfb9,
+	0xbe1db1, 0x54de6e8, 0xd4707f2, 0x8ebcc2d, 0x2c77056, 0x1568ce4, 0x15fcc849, 0x4069712, 0xe2ed85f,
+	0x2c5ff09, 0x42a6929, 0x628e7ea, 0xbd5b355, 0xaf0bd79, 0xaa03699, 0xdb99816, 0x4379cef, 0x81d57b,
+	0x11237f01, 0xe2a820b, 0xfd53b95, 0x6beb5ee, 0x1aeb790c, 0xe470d53, 0x2c2cfee, 0x1c1d8d8, 0xa520fc4,
+	0x1518e034, 0xa584dd4, 0x29e572b, 0xd4594fc, 0x141a8f6f, 0x8dfccf3, 0x5d20ba3, 0x2eb60c3, 0x9f16eb0,
+	0x11cec356, 0xf039f84, 0x1b0990c1, 0xc91e526, 0x10b65bae, 0xf0616e8, 0x173fa3ff, 0xec8ccf9, 0xbe32790,
+	0x11da3e79, 0xe2f35c7, 0x908875c, 0xdacf7bd, 0x538c165, 0x8d1487f, 0x7c31aed, 0x21af228, 0x7e1689d,
+	0xdfc23ca, 0x24f15dc, 0x25ef3c4, 0x35248cd, 0x99a0f43, 0xa4b6ecc, 0xd066b3, 0x2481152, 0x37a7688,
+	0x15a444b6, 0xb62300c, 0x4b841b, 0xa655e79, 0xd53226d, 0xbeb348a, 0x127f3c2, 0xb989247, 0x71a277d,
+	0x19e9dfcb, 0xb8f92d0, 0xe2d226c, 0x390a8b0, 0x183cc462, 0x7bd8167, 0x1f32a552, 0x5e02db4, 0xa146ee9,
+	0x1a003957, 0x1c95f61, 0x1eeec155, 0x26f811f, 0xf9596ba, 0x3082bfb, 0x96df083, 0x3e3a289, 0x7e2d8be,
+	0x157a63e0, 0x99b8941, 0x1da7d345, 0xcc6cd0, 0x10beed9a, 0x48e83c0, 0x13aa2e25, 0x7cad710, 0x4029988,
+	0x13dfa9dd, 0xb94f884, 0x1f4adfef, 0xb88543, 0x16f5f8dc, 0xa6a67f4, 0x14e274e2, 0x5e56cf4, 0x2f24ef,
+	0x1e9ef967, 0xfe09bad, 0xfe079b3, 0xcc0ae9e, 0xb3edf6d, 0x3e961bc, 0x130d7831, 0x31043d6, 0xba986f9,
+	0x1d28055, 0x65240ca, 0x4971fa3, 0x81b17f8, 0x11ec34a5, 0x8366ddc, 0x1471809, 0xfa5f1c6, 0xc911e15,
+	0x8849491, 0xcf4c2e2, 0x14471b91, 0x39f75be, 0x445c21e, 0xf1585e9, 0x72cc11f, 0x4c79f0c, 0xe5522e1,
+	0x1874c1ee, 0x4444211, 0x7914884, 0x3d1b133, 0x25ba3c, 0x4194f65, 0x1c0457ef, 0xac4899d, 0xe1fa66c,
+	0x130a7918, 0x9b8d312, 0x4b1c5c8, 0x61ccac3, 0x18c8aa6f, 0xe93cb0a, 0xdccb12c, 0xde10825, 0x969737d,
+	0xf58c0c3, 0x7cee6a9, 0xc2c329a, 0xc7f9ed9, 0x107b3981, 0x696a40e, 0x152847ff, 0x4d88754, 0xb141f47,
+	0x5a16ffe, 0x3a7870a, 0x18667659, 0x3b72b03, 0xb1c9435, 0x9285394, 0xa00005a, 0x37506c, 0x2edc0bb,
+	0x19afe392, 0xeb39cac, 0x177ef286, 0xdf87197, 0x19f844ed, 0x31fe8, 0x15f9bfd, 0x80dbec, 0x342e96e,
+	0x497aced, 0xe88e909, 0x1f5fa9ba, 0x530a6ee, 0x1ef4e3f1, 0x69ffd12, 0x583006d, 0x2ecc9b1, 0x362db70,
+	0x18c7bdc5, 0xf4bb3c5, 0x1c90b957, 0xf067c09, 0x9768f2b, 0xf73566a, 0x1939a900, 0x198c38a, 0x202a2a1,
+	0x4bbf5a6, 0x4e265bc, 0x1f44b6e7, 0x185ca49, 0xa39e81b, 0x24aff5b, 0x4acc9c2, 0x638bdd3, 0xb65b2a8,
+	0x6def8be, 0xb94537a, 0x10b81dee, 0xe00ec55, 0x2f2cdf7, 0xc20622d, 0x2d20f36, 0xe03c8c9, 0x898ea76,
+	0x8e3921b, 0x8905bff, 0x1e94b6c8, 0xee7ad86, 0x154797f2, 0xa620863, 0x3fbd0d9, 0x1f3caab, 0x30c24bd,
+	0x19d3892f, 0x59c17a2, 0x1ab4b0ae, 0xf8714ee, 0x90c4098, 0xa9c800d, 0x1910236b, 0xea808d3, 0x9ae2f31,
+	0x1a15ad64, 0xa48c8d1, 0x184635a4, 0xb725ef1, 0x11921dcc, 0x3f866df, 0x16c27568, 0xbdf580a, 0xb08f55c,
+	0x186ee1c, 0xb1627fa, 0x34e82f6, 0x933837e, 0xf311be5, 0xfedb03b, 0x167f72cd, 0xa5469c0, 0x9c82531,
+	0xb92a24b, 0x14fdc8b, 0x141980d1, 0xbdc3a49, 0x7e02bb1, 0xaf4e6dd, 0x106d99e1, 0xd4616fc, 0x93c2717,
+	0x1c0a0507, 0xc6d5fed, 0x9a03d8b, 0xa1d22b0, 0x127853e3, 0xc4ac6b8, 0x1a048cf7, 0x9afb72c, 0x65d485d,
+	0x72d5998, 0xe9fa744, 0xe49e82c, 0x253cf80, 0x5f777ce, 0xa3799a5, 0x17270cbb, 0xc1d1ef0, 0xdf74977,
+	0x114cb859, 0xfa8e037, 0xb8f3fe5, 0xc734cc6, 0x70d3d61, 0xeadac62, 0x12093dd0, 0x9add67d, 0x87200d6,
+	0x175bcbb, 0xb29b49f, 0x1806b79c, 0x12fb61f, 0x170b3a10, 0x3aaf1cf, 0xa224085, 0x79d26af, 0x97759e2,
+	0x92e19f1, 0xb32714d, 0x1f00d9f1, 0xc728619, 0x9e6f627, 0xe745e24, 0x18ea4ace, 0xfc60a41, 0x125f5b2,
+	0xc3cf512, 0x39ed486, 0xf4d15fa, 0xf9167fd, 0x1c1f5dd5, 0xc21a53e, 0x1897930, 0x957a112, 0x21059a0,
+	0x1f9e3ddc, 0xa4dfced, 0x8427f6f, 0x726fbe7, 0x1ea658f8, 0x2fdcd4c, 0x17e9b66f, 0xb2e7c2e, 0x39923bf,
+	0x1bae104, 0x3973ce5, 0xc6f264c, 0x3511b84, 0x124195d7, 0x11996bd, 0x20be23d, 0xdc437c4, 0x4b4f16b,
+	0x11902a0, 0x6c29cc9, 0x1d5ffbe6, 0xdb0b4c7, 0x10144c14, 0x2f2b719, 0x301189, 0x2343336, 0xa0bf2ac,
+}
+
+func sm2P256GetScalar(b *[32]byte, a []byte) {
+	var scalarBytes []byte
+
+	n := new(big.Int).SetBytes(a)
+	if n.Cmp(sm2P256.N) >= 0 {
+		n.Mod(n, sm2P256.N)
+		scalarBytes = n.Bytes()
+	} else {
+		scalarBytes = a
+	}
+	for i, v := range scalarBytes {
+		b[len(scalarBytes)-(1+i)] = v
+	}
+}
+
+func sm2P256PointAddMixed(xOut, yOut, zOut, x1, y1, z1, x2, y2 *sm2P256FieldElement) {
+	var z1z1, z1z1z1, s2, u2, h, i, j, r, rr, v, tmp sm2P256FieldElement
+
+	sm2P256Square(&z1z1, z1)
+	sm2P256Add(&tmp, z1, z1)
+
+	sm2P256Mul(&u2, x2, &z1z1)
+	sm2P256Mul(&z1z1z1, z1, &z1z1)
+	sm2P256Mul(&s2, y2, &z1z1z1)
+	sm2P256Sub(&h, &u2, x1)
+	sm2P256Add(&i, &h, &h)
+	sm2P256Square(&i, &i)
+	sm2P256Mul(&j, &h, &i)
+	sm2P256Sub(&r, &s2, y1)
+	sm2P256Add(&r, &r, &r)
+	sm2P256Mul(&v, x1, &i)
+
+	sm2P256Mul(zOut, &tmp, &h)
+	sm2P256Square(&rr, &r)
+	sm2P256Sub(xOut, &rr, &j)
+	sm2P256Sub(xOut, xOut, &v)
+	sm2P256Sub(xOut, xOut, &v)
+
+	sm2P256Sub(&tmp, &v, xOut)
+	sm2P256Mul(yOut, &tmp, &r)
+	sm2P256Mul(&tmp, y1, &j)
+	sm2P256Sub(yOut, yOut, &tmp)
+	sm2P256Sub(yOut, yOut, &tmp)
+}
+
+// sm2P256CopyConditional sets out=in if mask = 0xffffffff in constant time.
+//
+// On entry: mask is either 0 or 0xffffffff.
+func sm2P256CopyConditional(out, in *sm2P256FieldElement, mask uint32) {
+	for i := 0; i < 9; i++ {
+		tmp := mask & (in[i] ^ out[i])
+		out[i] ^= tmp
+	}
+}
+
+// sm2P256SelectAffinePoint sets {out_x,out_y} to the index'th entry of table.
+// On entry: index < 16, table[0] must be zero.
+func sm2P256SelectAffinePoint(xOut, yOut *sm2P256FieldElement, table []uint32, index uint32) {
+	for i := range xOut {
+		xOut[i] = 0
+	}
+	for i := range yOut {
+		yOut[i] = 0
+	}
+
+	for i := uint32(1); i < 16; i++ {
+		mask := i ^ index
+		mask |= mask >> 2
+		mask |= mask >> 1
+		mask &= 1
+		mask--
+		for j := range xOut {
+			xOut[j] |= table[0] & mask
+			table = table[1:]
+		}
+		for j := range yOut {
+			yOut[j] |= table[0] & mask
+			table = table[1:]
+		}
+	}
+}
+
+// sm2P256SelectJacobianPoint sets {out_x,out_y,out_z} to the index'th entry of
+// table.
+// On entry: index < 16, table[0] must be zero.
+func sm2P256SelectJacobianPoint(xOut, yOut, zOut *sm2P256FieldElement, table *[16][3]sm2P256FieldElement, index uint32) {
+	for i := range xOut {
+		xOut[i] = 0
+	}
+	for i := range yOut {
+		yOut[i] = 0
+	}
+	for i := range zOut {
+		zOut[i] = 0
+	}
+
+	// The implicit value at index 0 is all zero. We don't need to perform that
+	// iteration of the loop because we already set out_* to zero.
+	for i := uint32(1); i < 16; i++ {
+		mask := i ^ index
+		mask |= mask >> 2
+		mask |= mask >> 1
+		mask &= 1
+		mask--
+		for j := range xOut {
+			xOut[j] |= table[i][0][j] & mask
+		}
+		for j := range yOut {
+			yOut[j] |= table[i][1][j] & mask
+		}
+		for j := range zOut {
+			zOut[j] |= table[i][2][j] & mask
+		}
+	}
+}
+
+// sm2P256GetBit returns the bit'th bit of scalar.
+func sm2P256GetBit(scalar *[32]uint8, bit uint) uint32 {
+	return uint32(((scalar[bit>>3]) >> (bit & 7)) & 1)
+}
+
+// sm2P256ScalarBaseMult sets {xOut,yOut,zOut} = scalar*G where scalar is a
+// little-endian number. Note that the value of scalar must be less than the
+// order of the group.
+func sm2P256ScalarBaseMult(xOut, yOut, zOut *sm2P256FieldElement, scalar *[32]uint8) {
+	nIsInfinityMask := ^uint32(0)
+	var px, py, tx, ty, tz sm2P256FieldElement
+	var pIsNoninfiniteMask, mask, tableOffset uint32
+
+	for i := range xOut {
+		xOut[i] = 0
+	}
+	for i := range yOut {
+		yOut[i] = 0
+	}
+	for i := range zOut {
+		zOut[i] = 0
+	}
+
+	// The loop adds bits at positions 0, 64, 128 and 192, followed by
+	// positions 32,96,160 and 224 and does this 32 times.
+	for i := uint(0); i < 32; i++ {
+		if i != 0 {
+			sm2P256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut)
+		}
+		tableOffset = 0
+		for j := uint(0); j <= 32; j += 32 {
+			bit0 := sm2P256GetBit(scalar, 31-i+j)
+			bit1 := sm2P256GetBit(scalar, 95-i+j)
+			bit2 := sm2P256GetBit(scalar, 159-i+j)
+			bit3 := sm2P256GetBit(scalar, 223-i+j)
+			index := bit0 | (bit1 << 1) | (bit2 << 2) | (bit3 << 3)
+
+			sm2P256SelectAffinePoint(&px, &py, sm2P256Precomputed[tableOffset:], index)
+			tableOffset += 30 * 9
+
+			// Since scalar is less than the order of the group, we know that
+			// {xOut,yOut,zOut} != {px,py,1}, unless both are zero, which we handle
+			// below.
+			sm2P256PointAddMixed(&tx, &ty, &tz, xOut, yOut, zOut, &px, &py)
+			// The result of pointAddMixed is incorrect if {xOut,yOut,zOut} is zero
+			// (a.k.a.  the point at infinity). We handle that situation by
+			// copying the point from the table.
+			sm2P256CopyConditional(xOut, &px, nIsInfinityMask)
+			sm2P256CopyConditional(yOut, &py, nIsInfinityMask)
+			sm2P256CopyConditional(zOut, &sm2P256Factor[1], nIsInfinityMask)
+
+			// Equally, the result is also wrong if the point from the table is
+			// zero, which happens when the index is zero. We handle that by
+			// only copying from {tx,ty,tz} to {xOut,yOut,zOut} if index != 0.
+			pIsNoninfiniteMask = nonZeroToAllOnes(index)
+			mask = pIsNoninfiniteMask & ^nIsInfinityMask
+			sm2P256CopyConditional(xOut, &tx, mask)
+			sm2P256CopyConditional(yOut, &ty, mask)
+			sm2P256CopyConditional(zOut, &tz, mask)
+			// If p was not zero, then n is now non-zero.
+			nIsInfinityMask &^= pIsNoninfiniteMask
+		}
+	}
+}
+
+func sm2P256ScalarMult(xOut, yOut, zOut, x, y *sm2P256FieldElement, scalar *[32]uint8) {
+	var precomp [16][3]sm2P256FieldElement
+	var px, py, pz, tx, ty, tz sm2P256FieldElement
+	var nIsInfinityMask, index, pIsNoninfiniteMask, mask uint32
+
+	// We precompute 0,1,2,... times {x,y}.
+	precomp[1][0] = *x
+	precomp[1][1] = *y
+	precomp[1][2] = sm2P256Factor[1]
+
+	for i := 2; i < 16; i += 2 {
+		sm2P256PointDouble(&precomp[i][0], &precomp[i][1], &precomp[i][2], &precomp[i/2][0], &precomp[i/2][1], &precomp[i/2][2])
+		sm2P256PointAddMixed(&precomp[i+1][0], &precomp[i+1][1], &precomp[i+1][2], &precomp[i][0], &precomp[i][1], &precomp[i][2], x, y)
+	}
+
+	for i := range xOut {
+		xOut[i] = 0
+	}
+	for i := range yOut {
+		yOut[i] = 0
+	}
+	for i := range zOut {
+		zOut[i] = 0
+	}
+	nIsInfinityMask = ^uint32(0)
+
+	// We add in a window of four bits each iteration and do this 64 times.
+	for i := 0; i < 64; i++ {
+		if i != 0 {
+			sm2P256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut)
+			sm2P256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut)
+			sm2P256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut)
+			sm2P256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut)
+		}
+
+		index = uint32(scalar[31-i/2])
+		if (i & 1) == 1 {
+			index &= 15
+		} else {
+			index >>= 4
+		}
+
+		// See the comments in scalarBaseMult about handling infinities.
+		sm2P256SelectJacobianPoint(&px, &py, &pz, &precomp, index)
+		sm2P256PointAdd(xOut, yOut, zOut, &px, &py, &pz, &tx, &ty, &tz)
+		sm2P256CopyConditional(xOut, &px, nIsInfinityMask)
+		sm2P256CopyConditional(yOut, &py, nIsInfinityMask)
+		sm2P256CopyConditional(zOut, &pz, nIsInfinityMask)
+
+		pIsNoninfiniteMask = nonZeroToAllOnes(index)
+		mask = pIsNoninfiniteMask & ^nIsInfinityMask
+		sm2P256CopyConditional(xOut, &tx, mask)
+		sm2P256CopyConditional(yOut, &ty, mask)
+		sm2P256CopyConditional(zOut, &tz, mask)
+		nIsInfinityMask &^= pIsNoninfiniteMask
+	}
+}
+
+func sm2P256PointToAffine(xOut, yOut, x, y, z *sm2P256FieldElement) {
+	var zInv, zInvSq sm2P256FieldElement
+
+	zz := sm2P256ToBig(z)
+	zz.ModInverse(zz, sm2P256.P)
+	sm2P256FromBig(&zInv, zz)
+
+	sm2P256Square(&zInvSq, &zInv)
+	sm2P256Mul(xOut, x, &zInvSq)
+	sm2P256Mul(&zInv, &zInv, &zInvSq)
+	sm2P256Mul(yOut, y, &zInv)
+}
+
+func sm2P256ToAffine(x, y, z *sm2P256FieldElement) (xOut, yOut *big.Int) {
+	var xx, yy sm2P256FieldElement
+
+	sm2P256PointToAffine(&xx, &yy, x, y, z)
+	return sm2P256ToBig(&xx), sm2P256ToBig(&yy)
+}
+
+var sm2P256Factor = []sm2P256FieldElement{
+	sm2P256FieldElement{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
+	sm2P256FieldElement{0x2, 0x0, 0x1FFFFF00, 0x7FF, 0x0, 0x0, 0x0, 0x2000000, 0x0},
+	sm2P256FieldElement{0x4, 0x0, 0x1FFFFE00, 0xFFF, 0x0, 0x0, 0x0, 0x4000000, 0x0},
+	sm2P256FieldElement{0x6, 0x0, 0x1FFFFD00, 0x17FF, 0x0, 0x0, 0x0, 0x6000000, 0x0},
+	sm2P256FieldElement{0x8, 0x0, 0x1FFFFC00, 0x1FFF, 0x0, 0x0, 0x0, 0x8000000, 0x0},
+	sm2P256FieldElement{0xA, 0x0, 0x1FFFFB00, 0x27FF, 0x0, 0x0, 0x0, 0xA000000, 0x0},
+	sm2P256FieldElement{0xC, 0x0, 0x1FFFFA00, 0x2FFF, 0x0, 0x0, 0x0, 0xC000000, 0x0},
+	sm2P256FieldElement{0xE, 0x0, 0x1FFFF900, 0x37FF, 0x0, 0x0, 0x0, 0xE000000, 0x0},
+	sm2P256FieldElement{0x10, 0x0, 0x1FFFF800, 0x3FFF, 0x0, 0x0, 0x0, 0x0, 0x01},
+}
+
+func sm2P256Scalar(b *sm2P256FieldElement, a int) {
+	sm2P256Mul(b, b, &sm2P256Factor[a])
+}
+
+// (x3, y3, z3) = (x1, y1, z1) + (x2, y2, z2)
+func sm2P256PointAdd(x1, y1, z1, x2, y2, z2, x3, y3, z3 *sm2P256FieldElement) {
+	var u1, u2, z22, z12, z23, z13, s1, s2, h, h2, r, r2, tm sm2P256FieldElement
+
+	if sm2P256ToBig(z1).Sign() == 0 {
+		sm2P256Dup(x3, x2)
+		sm2P256Dup(y3, y2)
+		sm2P256Dup(z3, z2)
+		return
+	}
+
+	if sm2P256ToBig(z2).Sign() == 0 {
+		sm2P256Dup(x3, x1)
+		sm2P256Dup(y3, y1)
+		sm2P256Dup(z3, z1)
+		return
+	}
+
+	sm2P256Square(&z12, z1) // z12 = z1 ^ 2
+	sm2P256Square(&z22, z2) // z22 = z2 ^ 2
+
+	sm2P256Mul(&z13, &z12, z1) // z13 = z1 ^ 3
+	sm2P256Mul(&z23, &z22, z2) // z23 = z2 ^ 3
+
+	sm2P256Mul(&u1, x1, &z22) // u1 = x1 * z2 ^ 2
+	sm2P256Mul(&u2, x2, &z12) // u2 = x2 * z1 ^ 2
+
+	sm2P256Mul(&s1, y1, &z23) // s1 = y1 * z2 ^ 3
+	sm2P256Mul(&s2, y2, &z13) // s2 = y2 * z1 ^ 3
+
+	if sm2P256ToBig(&u1).Cmp(sm2P256ToBig(&u2)) == 0 &&
+		sm2P256ToBig(&s1).Cmp(sm2P256ToBig(&s2)) == 0 {
+		sm2P256PointDouble(x1, y1, z1, x1, y1, z1)
+	}
+
+	sm2P256Sub(&h, &u2, &u1) // h = u2 - u1
+	sm2P256Sub(&r, &s2, &s1) // r = s2 - s1
+
+	sm2P256Square(&r2, &r) // r2 = r ^ 2
+	sm2P256Square(&h2, &h) // h2 = h ^ 2
+
+	sm2P256Mul(&tm, &h2, &h) // tm = h ^ 3
+	sm2P256Sub(x3, &r2, &tm)
+	sm2P256Mul(&tm, &u1, &h2)
+	sm2P256Scalar(&tm, 2)   // tm = 2 * (u1 * h ^ 2)
+	sm2P256Sub(x3, x3, &tm) // x3 = r ^ 2 - h ^ 3 - 2 * u1 * h ^ 2
+
+	sm2P256Mul(&tm, &u1, &h2) // tm = u1 * h ^ 2
+	sm2P256Sub(&tm, &tm, x3)  // tm = u1 * h ^ 2 - x3
+	sm2P256Mul(y3, &r, &tm)
+	sm2P256Mul(&tm, &h2, &h)  // tm = h ^ 3
+	sm2P256Mul(&tm, &tm, &s1) // tm = s1 * h ^ 3
+	sm2P256Sub(y3, y3, &tm)   // y3 = r * (u1 * h ^ 2 - x3) - s1 * h ^ 3
+
+	sm2P256Mul(z3, z1, z2)
+	sm2P256Mul(z3, z3, &h) // z3 = z1 * z3 * h
+}
+
+func sm2P256PointDouble(x3, y3, z3, x, y, z *sm2P256FieldElement) {
+	var s, m, m2, x2, y2, z2, z4, y4, az4 sm2P256FieldElement
+
+	sm2P256Square(&x2, x) // x2 = x ^ 2
+	sm2P256Square(&y2, y) // y2 = y ^ 2
+	sm2P256Square(&z2, z) // z2 = z ^ 2
+
+	sm2P256Square(&z4, z)   // z4 = z ^ 2
+	sm2P256Mul(&z4, &z4, z) // z4 = z ^ 3
+	sm2P256Mul(&z4, &z4, z) // z4 = z ^ 4
+
+	sm2P256Square(&y4, y)   // y4 = y ^ 2
+	sm2P256Mul(&y4, &y4, y) // y4 = y ^ 3
+	sm2P256Mul(&y4, &y4, y) // y4 = y ^ 4
+	sm2P256Scalar(&y4, 8)   // y4 = 8 * y ^ 4
+
+	sm2P256Mul(&s, x, &y2)
+	sm2P256Scalar(&s, 4) // s = 4 * x * y ^ 2
+
+	sm2P256Dup(&m, &x2)
+	sm2P256Scalar(&m, 3)
+	sm2P256Mul(&az4, &sm2P256.a, &z4)
+	sm2P256Add(&m, &m, &az4) // m = 3 * x ^ 2 + a * z ^ 4
+
+	sm2P256Square(&m2, &m) // m2 = m ^ 2
+
+	sm2P256Add(z3, y, z)
+	sm2P256Square(z3, z3)
+	sm2P256Sub(z3, z3, &z2)
+	sm2P256Sub(z3, z3, &y2) // z' = (y + z) ^2 - z ^ 2 - y ^ 2
+
+	sm2P256Sub(x3, &m2, &s)
+	sm2P256Sub(x3, x3, &s) // x' = m2 - 2 * s
+
+	sm2P256Sub(y3, &s, x3)
+	sm2P256Mul(y3, y3, &m)
+	sm2P256Sub(y3, y3, &y4) // y' = m * (s - x') - 8 * y ^ 4
+}
+
+// p256Zero31 is 0 mod p.
+var sm2P256Zero31 = sm2P256FieldElement{0x7FFFFFF8, 0x3FFFFFFC, 0x800003FC, 0x3FFFDFFC, 0x7FFFFFFC, 0x3FFFFFFC, 0x7FFFFFFC, 0x37FFFFFC, 0x7FFFFFFC}
+
+// c = a + b
+func sm2P256Add(c, a, b *sm2P256FieldElement) {
+	carry := uint32(0)
+	for i := 0; ; i++ {
+		c[i] = a[i] + b[i]
+		c[i] += carry
+		carry = c[i] >> 29
+		c[i] &= bottom29Bits
+		i++
+		if i == 9 {
+			break
+		}
+		c[i] = a[i] + b[i]
+		c[i] += carry
+		carry = c[i] >> 28
+		c[i] &= bottom28Bits
+	}
+	sm2P256ReduceCarry(c, carry)
+}
+
+// c = a - b
+func sm2P256Sub(c, a, b *sm2P256FieldElement) {
+	var carry uint32
+
+	for i := 0; ; i++ {
+		c[i] = a[i] - b[i]
+		c[i] += sm2P256Zero31[i]
+		c[i] += carry
+		carry = c[i] >> 29
+		c[i] &= bottom29Bits
+		i++
+		if i == 9 {
+			break
+		}
+		c[i] = a[i] - b[i]
+		c[i] += sm2P256Zero31[i]
+		c[i] += carry
+		carry = c[i] >> 28
+		c[i] &= bottom28Bits
+	}
+	sm2P256ReduceCarry(c, carry)
+}
+
+// c = a * b
+func sm2P256Mul(c, a, b *sm2P256FieldElement) {
+	var tmp sm2P256LargeFieldElement
+
+	tmp[0] = uint64(a[0]) * uint64(b[0])
+	tmp[1] = uint64(a[0])*(uint64(b[1])<<0) +
+		uint64(a[1])*(uint64(b[0])<<0)
+	tmp[2] = uint64(a[0])*(uint64(b[2])<<0) +
+		uint64(a[1])*(uint64(b[1])<<1) +
+		uint64(a[2])*(uint64(b[0])<<0)
+	tmp[3] = uint64(a[0])*(uint64(b[3])<<0) +
+		uint64(a[1])*(uint64(b[2])<<0) +
+		uint64(a[2])*(uint64(b[1])<<0) +
+		uint64(a[3])*(uint64(b[0])<<0)
+	tmp[4] = uint64(a[0])*(uint64(b[4])<<0) +
+		uint64(a[1])*(uint64(b[3])<<1) +
+		uint64(a[2])*(uint64(b[2])<<0) +
+		uint64(a[3])*(uint64(b[1])<<1) +
+		uint64(a[4])*(uint64(b[0])<<0)
+	tmp[5] = uint64(a[0])*(uint64(b[5])<<0) +
+		uint64(a[1])*(uint64(b[4])<<0) +
+		uint64(a[2])*(uint64(b[3])<<0) +
+		uint64(a[3])*(uint64(b[2])<<0) +
+		uint64(a[4])*(uint64(b[1])<<0) +
+		uint64(a[5])*(uint64(b[0])<<0)
+	tmp[6] = uint64(a[0])*(uint64(b[6])<<0) +
+		uint64(a[1])*(uint64(b[5])<<1) +
+		uint64(a[2])*(uint64(b[4])<<0) +
+		uint64(a[3])*(uint64(b[3])<<1) +
+		uint64(a[4])*(uint64(b[2])<<0) +
+		uint64(a[5])*(uint64(b[1])<<1) +
+		uint64(a[6])*(uint64(b[0])<<0)
+	tmp[7] = uint64(a[0])*(uint64(b[7])<<0) +
+		uint64(a[1])*(uint64(b[6])<<0) +
+		uint64(a[2])*(uint64(b[5])<<0) +
+		uint64(a[3])*(uint64(b[4])<<0) +
+		uint64(a[4])*(uint64(b[3])<<0) +
+		uint64(a[5])*(uint64(b[2])<<0) +
+		uint64(a[6])*(uint64(b[1])<<0) +
+		uint64(a[7])*(uint64(b[0])<<0)
+	// tmp[8] has the greatest value but doesn't overflow. See logic in
+	// p256Square.
+	tmp[8] = uint64(a[0])*(uint64(b[8])<<0) +
+		uint64(a[1])*(uint64(b[7])<<1) +
+		uint64(a[2])*(uint64(b[6])<<0) +
+		uint64(a[3])*(uint64(b[5])<<1) +
+		uint64(a[4])*(uint64(b[4])<<0) +
+		uint64(a[5])*(uint64(b[3])<<1) +
+		uint64(a[6])*(uint64(b[2])<<0) +
+		uint64(a[7])*(uint64(b[1])<<1) +
+		uint64(a[8])*(uint64(b[0])<<0)
+	tmp[9] = uint64(a[1])*(uint64(b[8])<<0) +
+		uint64(a[2])*(uint64(b[7])<<0) +
+		uint64(a[3])*(uint64(b[6])<<0) +
+		uint64(a[4])*(uint64(b[5])<<0) +
+		uint64(a[5])*(uint64(b[4])<<0) +
+		uint64(a[6])*(uint64(b[3])<<0) +
+		uint64(a[7])*(uint64(b[2])<<0) +
+		uint64(a[8])*(uint64(b[1])<<0)
+	tmp[10] = uint64(a[2])*(uint64(b[8])<<0) +
+		uint64(a[3])*(uint64(b[7])<<1) +
+		uint64(a[4])*(uint64(b[6])<<0) +
+		uint64(a[5])*(uint64(b[5])<<1) +
+		uint64(a[6])*(uint64(b[4])<<0) +
+		uint64(a[7])*(uint64(b[3])<<1) +
+		uint64(a[8])*(uint64(b[2])<<0)
+	tmp[11] = uint64(a[3])*(uint64(b[8])<<0) +
+		uint64(a[4])*(uint64(b[7])<<0) +
+		uint64(a[5])*(uint64(b[6])<<0) +
+		uint64(a[6])*(uint64(b[5])<<0) +
+		uint64(a[7])*(uint64(b[4])<<0) +
+		uint64(a[8])*(uint64(b[3])<<0)
+	tmp[12] = uint64(a[4])*(uint64(b[8])<<0) +
+		uint64(a[5])*(uint64(b[7])<<1) +
+		uint64(a[6])*(uint64(b[6])<<0) +
+		uint64(a[7])*(uint64(b[5])<<1) +
+		uint64(a[8])*(uint64(b[4])<<0)
+	tmp[13] = uint64(a[5])*(uint64(b[8])<<0) +
+		uint64(a[6])*(uint64(b[7])<<0) +
+		uint64(a[7])*(uint64(b[6])<<0) +
+		uint64(a[8])*(uint64(b[5])<<0)
+	tmp[14] = uint64(a[6])*(uint64(b[8])<<0) +
+		uint64(a[7])*(uint64(b[7])<<1) +
+		uint64(a[8])*(uint64(b[6])<<0)
+	tmp[15] = uint64(a[7])*(uint64(b[8])<<0) +
+		uint64(a[8])*(uint64(b[7])<<0)
+	tmp[16] = uint64(a[8]) * (uint64(b[8]) << 0)
+	sm2P256ReduceDegree(c, &tmp)
+}
+
+// b = a * a
+func sm2P256Square(b, a *sm2P256FieldElement) {
+	var tmp sm2P256LargeFieldElement
+
+	tmp[0] = uint64(a[0]) * uint64(a[0])
+	tmp[1] = uint64(a[0]) * (uint64(a[1]) << 1)
+	tmp[2] = uint64(a[0])*(uint64(a[2])<<1) +
+		uint64(a[1])*(uint64(a[1])<<1)
+	tmp[3] = uint64(a[0])*(uint64(a[3])<<1) +
+		uint64(a[1])*(uint64(a[2])<<1)
+	tmp[4] = uint64(a[0])*(uint64(a[4])<<1) +
+		uint64(a[1])*(uint64(a[3])<<2) +
+		uint64(a[2])*uint64(a[2])
+	tmp[5] = uint64(a[0])*(uint64(a[5])<<1) +
+		uint64(a[1])*(uint64(a[4])<<1) +
+		uint64(a[2])*(uint64(a[3])<<1)
+	tmp[6] = uint64(a[0])*(uint64(a[6])<<1) +
+		uint64(a[1])*(uint64(a[5])<<2) +
+		uint64(a[2])*(uint64(a[4])<<1) +
+		uint64(a[3])*(uint64(a[3])<<1)
+	tmp[7] = uint64(a[0])*(uint64(a[7])<<1) +
+		uint64(a[1])*(uint64(a[6])<<1) +
+		uint64(a[2])*(uint64(a[5])<<1) +
+		uint64(a[3])*(uint64(a[4])<<1)
+	// tmp[8] has the greatest value of 2**61 + 2**60 + 2**61 + 2**60 + 2**60,
+	// which is < 2**64 as required.
+	tmp[8] = uint64(a[0])*(uint64(a[8])<<1) +
+		uint64(a[1])*(uint64(a[7])<<2) +
+		uint64(a[2])*(uint64(a[6])<<1) +
+		uint64(a[3])*(uint64(a[5])<<2) +
+		uint64(a[4])*uint64(a[4])
+	tmp[9] = uint64(a[1])*(uint64(a[8])<<1) +
+		uint64(a[2])*(uint64(a[7])<<1) +
+		uint64(a[3])*(uint64(a[6])<<1) +
+		uint64(a[4])*(uint64(a[5])<<1)
+	tmp[10] = uint64(a[2])*(uint64(a[8])<<1) +
+		uint64(a[3])*(uint64(a[7])<<2) +
+		uint64(a[4])*(uint64(a[6])<<1) +
+		uint64(a[5])*(uint64(a[5])<<1)
+	tmp[11] = uint64(a[3])*(uint64(a[8])<<1) +
+		uint64(a[4])*(uint64(a[7])<<1) +
+		uint64(a[5])*(uint64(a[6])<<1)
+	tmp[12] = uint64(a[4])*(uint64(a[8])<<1) +
+		uint64(a[5])*(uint64(a[7])<<2) +
+		uint64(a[6])*uint64(a[6])
+	tmp[13] = uint64(a[5])*(uint64(a[8])<<1) +
+		uint64(a[6])*(uint64(a[7])<<1)
+	tmp[14] = uint64(a[6])*(uint64(a[8])<<1) +
+		uint64(a[7])*(uint64(a[7])<<1)
+	tmp[15] = uint64(a[7]) * (uint64(a[8]) << 1)
+	tmp[16] = uint64(a[8]) * uint64(a[8])
+	sm2P256ReduceDegree(b, &tmp)
+}
+
+// nonZeroToAllOnes returns:
+//   0xffffffff for 0 < x <= 2**31
+//   0 for x == 0 or x > 2**31.
+func nonZeroToAllOnes(x uint32) uint32 {
+	return ((x - 1) >> 31) - 1
+}
+
+var sm2P256Carry = [8 * 9]uint32{
+	0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+	0x2, 0x0, 0x1FFFFF00, 0x7FF, 0x0, 0x0, 0x0, 0x2000000, 0x0,
+	0x4, 0x0, 0x1FFFFE00, 0xFFF, 0x0, 0x0, 0x0, 0x4000000, 0x0,
+	0x6, 0x0, 0x1FFFFD00, 0x17FF, 0x0, 0x0, 0x0, 0x6000000, 0x0,
+	0x8, 0x0, 0x1FFFFC00, 0x1FFF, 0x0, 0x0, 0x0, 0x8000000, 0x0,
+	0xA, 0x0, 0x1FFFFB00, 0x27FF, 0x0, 0x0, 0x0, 0xA000000, 0x0,
+	0xC, 0x0, 0x1FFFFA00, 0x2FFF, 0x0, 0x0, 0x0, 0xC000000, 0x0,
+	0xE, 0x0, 0x1FFFF900, 0x37FF, 0x0, 0x0, 0x0, 0xE000000, 0x0,
+}
+
+// carry < 2 ^ 3
+func sm2P256ReduceCarry(a *sm2P256FieldElement, carry uint32) {
+	a[0] += sm2P256Carry[carry*9+0]
+	a[2] += sm2P256Carry[carry*9+2]
+	a[3] += sm2P256Carry[carry*9+3]
+	a[7] += sm2P256Carry[carry*9+7]
+}
+
+// 这代码真是丑比了，我也是对自己醉了。。。
+// 你最好别改这个代码，不然你会死的很惨。。
+func sm2P256ReduceDegree(a *sm2P256FieldElement, b *sm2P256LargeFieldElement) {
+	var tmp [18]uint32
+	var carry, x, xMask uint32
+
+	// tmp
+	// 0  | 1  | 2  | 3  | 4  | 5  | 6  | 7  | 8  |  9 | 10 ...
+	// 29 | 28 | 29 | 28 | 29 | 28 | 29 | 28 | 29 | 28 | 29 ...
+	tmp[0] = uint32(b[0]) & bottom29Bits
+	tmp[1] = uint32(b[0]) >> 29
+	tmp[1] |= (uint32(b[0]>>32) << 3) & bottom28Bits
+	tmp[1] += uint32(b[1]) & bottom28Bits
+	carry = tmp[1] >> 28
+	tmp[1] &= bottom28Bits
+	for i := 2; i < 17; i++ {
+		tmp[i] = (uint32(b[i-2] >> 32)) >> 25
+		tmp[i] += (uint32(b[i-1])) >> 28
+		tmp[i] += (uint32(b[i-1]>>32) << 4) & bottom29Bits
+		tmp[i] += uint32(b[i]) & bottom29Bits
+		tmp[i] += carry
+		carry = tmp[i] >> 29
+		tmp[i] &= bottom29Bits
+
+		i++
+		if i == 17 {
+			break
+		}
+		tmp[i] = uint32(b[i-2]>>32) >> 25
+		tmp[i] += uint32(b[i-1]) >> 29
+		tmp[i] += ((uint32(b[i-1] >> 32)) << 3) & bottom28Bits
+		tmp[i] += uint32(b[i]) & bottom28Bits
+		tmp[i] += carry
+		carry = tmp[i] >> 28
+		tmp[i] &= bottom28Bits
+	}
+	tmp[17] = uint32(b[15]>>32) >> 25
+	tmp[17] += uint32(b[16]) >> 29
+	tmp[17] += uint32(b[16]>>32) << 3
+	tmp[17] += carry
+
+	for i := 0; ; i += 2 {
+
+		tmp[i+1] += tmp[i] >> 29
+		x = tmp[i] & bottom29Bits
+		tmp[i] = 0
+		if x > 0 {
+			set4 := uint32(0)
+			set7 := uint32(0)
+			xMask = nonZeroToAllOnes(x)
+			tmp[i+2] += (x << 7) & bottom29Bits
+			tmp[i+3] += x >> 22
+			if tmp[i+3] < 0x10000000 {
+				set4 = 1
+				tmp[i+3] += 0x10000000 & xMask
+				tmp[i+3] -= (x << 10) & bottom28Bits
+			} else {
+				tmp[i+3] -= (x << 10) & bottom28Bits
+			}
+			if tmp[i+4] < 0x20000000 {
+				tmp[i+4] += 0x20000000 & xMask
+				tmp[i+4] -= set4 // 借位
+				tmp[i+4] -= x >> 18
+				if tmp[i+5] < 0x10000000 {
+					tmp[i+5] += 0x10000000 & xMask
+					tmp[i+5] -= 1 // 借位
+					if tmp[i+6] < 0x20000000 {
+						set7 = 1
+						tmp[i+6] += 0x20000000 & xMask
+						tmp[i+6] -= 1 // 借位
+					} else {
+						tmp[i+6] -= 1 // 借位
+					}
+				} else {
+					tmp[i+5] -= 1
+				}
+			} else {
+				tmp[i+4] -= set4 // 借位
+				tmp[i+4] -= x >> 18
+			}
+			if tmp[i+7] < 0x10000000 {
+				tmp[i+7] += 0x10000000 & xMask
+				tmp[i+7] -= set7
+				tmp[i+7] -= (x << 24) & bottom28Bits
+				tmp[i+8] += (x << 28) & bottom29Bits
+				if tmp[i+8] < 0x20000000 {
+					tmp[i+8] += 0x20000000 & xMask
+					tmp[i+8] -= 1
+					tmp[i+8] -= x >> 4
+					tmp[i+9] += ((x >> 1) - 1) & xMask
+				} else {
+					tmp[i+8] -= 1
+					tmp[i+8] -= x >> 4
+					tmp[i+9] += (x >> 1) & xMask
+				}
+			} else {
+				tmp[i+7] -= set7 // 借位
+				tmp[i+7] -= (x << 24) & bottom28Bits
+				tmp[i+8] += (x << 28) & bottom29Bits
+				if tmp[i+8] < 0x20000000 {
+					tmp[i+8] += 0x20000000 & xMask
+					tmp[i+8] -= x >> 4
+					tmp[i+9] += ((x >> 1) - 1) & xMask
+				} else {
+					tmp[i+8] -= x >> 4
+					tmp[i+9] += (x >> 1) & xMask
+				}
+			}
+
+		}
+
+		if i+1 == 9 {
+			break
+		}
+
+		tmp[i+2] += tmp[i+1] >> 28
+		x = tmp[i+1] & bottom28Bits
+		tmp[i+1] = 0
+		if x > 0 {
+			set5 := uint32(0)
+			set8 := uint32(0)
+			set9 := uint32(0)
+			xMask = nonZeroToAllOnes(x)
+			tmp[i+3] += (x << 7) & bottom28Bits
+			tmp[i+4] += x >> 21
+			if tmp[i+4] < 0x20000000 {
+				set5 = 1
+				tmp[i+4] += 0x20000000 & xMask
+				tmp[i+4] -= (x << 11) & bottom29Bits
+			} else {
+				tmp[i+4] -= (x << 11) & bottom29Bits
+			}
+			if tmp[i+5] < 0x10000000 {
+				tmp[i+5] += 0x10000000 & xMask
+				tmp[i+5] -= set5 // 借位
+				tmp[i+5] -= x >> 18
+				if tmp[i+6] < 0x20000000 {
+					tmp[i+6] += 0x20000000 & xMask
+					tmp[i+6] -= 1 // 借位
+					if tmp[i+7] < 0x10000000 {
+						set8 = 1
+						tmp[i+7] += 0x10000000 & xMask
+						tmp[i+7] -= 1 // 借位
+					} else {
+						tmp[i+7] -= 1 // 借位
+					}
+				} else {
+					tmp[i+6] -= 1 // 借位
+				}
+			} else {
+				tmp[i+5] -= set5 // 借位
+				tmp[i+5] -= x >> 18
+			}
+			if tmp[i+8] < 0x20000000 {
+				set9 = 1
+				tmp[i+8] += 0x20000000 & xMask
+				tmp[i+8] -= set8
+				tmp[i+8] -= (x << 25) & bottom29Bits
+			} else {
+				tmp[i+8] -= set8
+				tmp[i+8] -= (x << 25) & bottom29Bits
+			}
+			if tmp[i+9] < 0x10000000 {
+				tmp[i+9] += 0x10000000 & xMask
+				tmp[i+9] -= set9 // 借位
+				tmp[i+9] -= x >> 4
+				tmp[i+10] += (x - 1) & xMask
+			} else {
+				tmp[i+9] -= set9 // 借位
+				tmp[i+9] -= x >> 4
+				tmp[i+10] += x & xMask
+			}
+		}
+	}
+
+	carry = uint32(0)
+	for i := 0; i < 8; i++ {
+		a[i] = tmp[i+9]
+		a[i] += carry
+		a[i] += (tmp[i+10] << 28) & bottom29Bits
+		carry = a[i] >> 29
+		a[i] &= bottom29Bits
+
+		i++
+		a[i] = tmp[i+9] >> 1
+		a[i] += carry
+		carry = a[i] >> 28
+		a[i] &= bottom28Bits
+	}
+	a[8] = tmp[17]
+	a[8] += carry
+	carry = a[8] >> 29
+	a[8] &= bottom29Bits
+	sm2P256ReduceCarry(a, carry)
+}
+
+// b = a
+func sm2P256Dup(b, a *sm2P256FieldElement) {
+	*b = *a
+}
+
+// X = a * R mod P
+func sm2P256FromBig(X *sm2P256FieldElement, a *big.Int) {
+	x := new(big.Int).Lsh(a, 257)
+	x.Mod(x, sm2P256.P)
+	for i := 0; i < 9; i++ {
+		if bits := x.Bits(); len(bits) > 0 {
+			X[i] = uint32(bits[0]) & bottom29Bits
+		} else {
+			X[i] = 0
+		}
+		x.Rsh(x, 29)
+		i++
+		if i == 9 {
+			break
+		}
+		if bits := x.Bits(); len(bits) > 0 {
+			X[i] = uint32(bits[0]) & bottom28Bits
+		} else {
+			X[i] = 0
+		}
+		x.Rsh(x, 28)
+	}
+}
+
+// X = r * R mod P
+// r = X * R' mod P
+func sm2P256ToBig(X *sm2P256FieldElement) *big.Int {
+	r, tm := new(big.Int), new(big.Int)
+	r.SetInt64(int64(X[8]))
+	for i := 7; i >= 0; i-- {
+		if (i & 1) == 0 {
+			r.Lsh(r, 29)
+		} else {
+			r.Lsh(r, 28)
+		}
+		tm.SetInt64(int64(X[i]))
+		r.Add(r, tm)
+	}
+	r.Mul(r, sm2P256.RInverse)
+	r.Mod(r, sm2P256.P)
+	return r
+}
diff --git a/crypto/sm2/pkcs1.go b/crypto/sm2/pkcs1.go
new file mode 100644
index 00000000..8ef29b5f
--- /dev/null
+++ b/crypto/sm2/pkcs1.go
@@ -0,0 +1,132 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sm2
+
+import (
+	"crypto/rsa"
+	"encoding/asn1"
+	"errors"
+	"math/big"
+)
+
+// pkcs1PrivateKey is a structure which mirrors the PKCS#1 ASN.1 for an RSA private key.
+type pkcs1PrivateKey struct {
+	Version int
+	N       *big.Int
+	E       int
+	D       *big.Int
+	P       *big.Int
+	Q       *big.Int
+	// We ignore these values, if present, because rsa will calculate them.
+	Dp   *big.Int `asn1:"optional"`
+	Dq   *big.Int `asn1:"optional"`
+	Qinv *big.Int `asn1:"optional"`
+
+	AdditionalPrimes []pkcs1AdditionalRSAPrime `asn1:"optional,omitempty"`
+}
+
+type pkcs1AdditionalRSAPrime struct {
+	Prime *big.Int
+
+	// We ignore these values because rsa will calculate them.
+	Exp   *big.Int
+	Coeff *big.Int
+}
+
+// ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.
+func ParsePKCS1PrivateKey(der []byte) (*rsa.PrivateKey, error) {
+	var priv pkcs1PrivateKey
+	rest, err := asn1.Unmarshal(der, &priv)
+	if len(rest) > 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	if priv.Version > 1 {
+		return nil, errors.New("x509: unsupported private key version")
+	}
+
+	if priv.N.Sign() <= 0 || priv.D.Sign() <= 0 || priv.P.Sign() <= 0 || priv.Q.Sign() <= 0 {
+		return nil, errors.New("x509: private key contains zero or negative value")
+	}
+
+	key := new(rsa.PrivateKey)
+	key.PublicKey = rsa.PublicKey{
+		E: priv.E,
+		N: priv.N,
+	}
+
+	key.D = priv.D
+	key.Primes = make([]*big.Int, 2+len(priv.AdditionalPrimes))
+	key.Primes[0] = priv.P
+	key.Primes[1] = priv.Q
+	for i, a := range priv.AdditionalPrimes {
+		if a.Prime.Sign() <= 0 {
+			return nil, errors.New("x509: private key contains zero or negative prime")
+		}
+		key.Primes[i+2] = a.Prime
+		// We ignore the other two values because rsa will calculate
+		// them as needed.
+	}
+
+	err = key.Validate()
+	if err != nil {
+		return nil, err
+	}
+	key.Precompute()
+
+	return key, nil
+}
+
+// MarshalPKCS1PrivateKey converts a private key to ASN.1 DER encoded form.
+func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte {
+	key.Precompute()
+
+	version := 0
+	if len(key.Primes) > 2 {
+		version = 1
+	}
+
+	priv := pkcs1PrivateKey{
+		Version: version,
+		N:       key.N,
+		E:       key.PublicKey.E,
+		D:       key.D,
+		P:       key.Primes[0],
+		Q:       key.Primes[1],
+		Dp:      key.Precomputed.Dp,
+		Dq:      key.Precomputed.Dq,
+		Qinv:    key.Precomputed.Qinv,
+	}
+
+	priv.AdditionalPrimes = make([]pkcs1AdditionalRSAPrime, len(key.Precomputed.CRTValues))
+	for i, values := range key.Precomputed.CRTValues {
+		priv.AdditionalPrimes[i].Prime = key.Primes[2+i]
+		priv.AdditionalPrimes[i].Exp = values.Exp
+		priv.AdditionalPrimes[i].Coeff = values.Coeff
+	}
+
+	b, _ := asn1.Marshal(priv)
+	return b
+}
+
+// rsaPublicKey reflects the ASN.1 structure of a PKCS#1 public key.
+type rsaPublicKey struct {
+	N *big.Int
+	E int
+}
diff --git a/crypto/sm2/pkcs8.go b/crypto/sm2/pkcs8.go
new file mode 100644
index 00000000..192a664b
--- /dev/null
+++ b/crypto/sm2/pkcs8.go
@@ -0,0 +1,488 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sm2
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/elliptic"
+	"crypto/hmac"
+	"crypto/md5"
+	"crypto/rand"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/pem"
+	"errors"
+	"hash"
+	"io/ioutil"
+	"math/big"
+	"os"
+	"reflect"
+)
+
+/*
+ * reference to RFC5959 and RFC2898
+ */
+
+var (
+	oidPBES1  = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 5, 3}  // pbeWithMD5AndDES-CBC(PBES1)
+	oidPBES2  = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 5, 13} // id-PBES2(PBES2)
+	oidPBKDF2 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 5, 12} // id-PBKDF2
+
+	oidKEYMD5    = asn1.ObjectIdentifier{1, 2, 840, 113549, 2, 5}
+	oidKEYSHA1   = asn1.ObjectIdentifier{1, 2, 840, 113549, 2, 7}
+	oidKEYSHA256 = asn1.ObjectIdentifier{1, 2, 840, 113549, 2, 9}
+	oidKEYSHA512 = asn1.ObjectIdentifier{1, 2, 840, 113549, 2, 11}
+
+	oidAES128CBC = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 2}
+	oidAES256CBC = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 42}
+
+	oidSM2 = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
+)
+
+// reference to https://www.rfc-editor.org/rfc/rfc5958.txt
+type PrivateKeyInfo struct {
+	Version             int // v1 or v2
+	PrivateKeyAlgorithm []asn1.ObjectIdentifier
+	PrivateKey          []byte
+}
+
+// reference to https://www.rfc-editor.org/rfc/rfc5958.txt
+type EncryptedPrivateKeyInfo struct {
+	EncryptionAlgorithm Pbes2Algorithms
+	EncryptedData       []byte
+}
+
+// reference to https://www.ietf.org/rfc/rfc2898.txt
+type Pbes2Algorithms struct {
+	IdPBES2     asn1.ObjectIdentifier
+	Pbes2Params Pbes2Params
+}
+
+// reference to https://www.ietf.org/rfc/rfc2898.txt
+type Pbes2Params struct {
+	KeyDerivationFunc Pbes2KDfs // PBES2-KDFs
+	EncryptionScheme  Pbes2Encs // PBES2-Encs
+}
+
+// reference to https://www.ietf.org/rfc/rfc2898.txt
+type Pbes2KDfs struct {
+	IdPBKDF2    asn1.ObjectIdentifier
+	Pkdf2Params Pkdf2Params
+}
+
+type Pbes2Encs struct {
+	EncryAlgo asn1.ObjectIdentifier
+	IV        []byte
+}
+
+// reference to https://www.ietf.org/rfc/rfc2898.txt
+type Pkdf2Params struct {
+	Salt           []byte
+	IterationCount int
+	Prf            pkix.AlgorithmIdentifier
+}
+
+type sm2PrivateKey struct {
+	Version       int
+	PrivateKey    []byte
+	NamedCurveOID asn1.ObjectIdentifier `asn1:"optional,explicit,tag:0"`
+	PublicKey     asn1.BitString        `asn1:"optional,explicit,tag:1"`
+}
+
+type pkcs8 struct {
+	Version    int
+	Algo       pkix.AlgorithmIdentifier
+	PrivateKey []byte
+}
+
+// copy from crypto/pbkdf2.go
+func pbkdf(password, salt []byte, iter, keyLen int, h func() hash.Hash) []byte {
+	prf := hmac.New(h, password)
+	hashLen := prf.Size()
+	numBlocks := (keyLen + hashLen - 1) / hashLen
+
+	var buf [4]byte
+	dk := make([]byte, 0, numBlocks*hashLen)
+	U := make([]byte, hashLen)
+	for block := 1; block <= numBlocks; block++ {
+		// N.B.: || means concatenation, ^ means XOR
+		// for each block T_i = U_1 ^ U_2 ^ ... ^ U_iter
+		// U_1 = PRF(password, salt || uint(i))
+		prf.Reset()
+		prf.Write(salt)
+		buf[0] = byte(block >> 24)
+		buf[1] = byte(block >> 16)
+		buf[2] = byte(block >> 8)
+		buf[3] = byte(block)
+		prf.Write(buf[:4])
+		dk = prf.Sum(dk)
+		T := dk[len(dk)-hashLen:]
+		copy(U, T)
+
+		// U_n = PRF(password, U_(n-1))
+		for n := 2; n <= iter; n++ {
+			prf.Reset()
+			prf.Write(U)
+			U = U[:0]
+			U = prf.Sum(U)
+			for x := range U {
+				T[x] ^= U[x]
+			}
+		}
+	}
+	return dk[:keyLen]
+}
+
+func ParseSm2PublicKey(der []byte) (*PublicKey, error) {
+	var pubkey pkixPublicKey
+
+	if _, err := asn1.Unmarshal(der, &pubkey); err != nil {
+		return nil, err
+	}
+	if !reflect.DeepEqual(pubkey.Algo.Algorithm, oidSM2) {
+		return nil, errors.New("x509: not sm2 elliptic curve")
+	}
+	curve := P256Sm2()
+	x, y := elliptic.Unmarshal(curve, pubkey.BitString.Bytes)
+	pub := PublicKey{
+		Curve: curve,
+		X:     x,
+		Y:     y,
+	}
+	return &pub, nil
+}
+
+func MarshalSm2PublicKey(key *PublicKey) ([]byte, error) {
+	var r pkixPublicKey
+	var algo pkix.AlgorithmIdentifier
+
+	algo.Algorithm = oidSM2
+	algo.Parameters.Class = 0
+	algo.Parameters.Tag = 6
+	algo.Parameters.IsCompound = false
+	algo.Parameters.FullBytes = []byte{6, 8, 42, 129, 28, 207, 85, 1, 130, 45} // asn1.Marshal(asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 301})
+	r.Algo = algo
+	r.BitString = asn1.BitString{Bytes: elliptic.Marshal(key.Curve, key.X, key.Y)}
+	return asn1.Marshal(r)
+}
+
+func ParseSm2PrivateKey(der []byte) (*PrivateKey, error) {
+	var privKey sm2PrivateKey
+
+	if _, err := asn1.Unmarshal(der, &privKey); err != nil {
+		return nil, errors.New("x509: failed to parse SM2 private key: " + err.Error())
+	}
+	curve := P256Sm2()
+	k := new(big.Int).SetBytes(privKey.PrivateKey)
+	curveOrder := curve.Params().N
+	if k.Cmp(curveOrder) >= 0 {
+		return nil, errors.New("x509: invalid elliptic curve private key value")
+	}
+	priv := new(PrivateKey)
+	priv.Curve = curve
+	priv.D = k
+	privateKey := make([]byte, (curveOrder.BitLen()+7)/8)
+	for len(privKey.PrivateKey) > len(privateKey) {
+		if privKey.PrivateKey[0] != 0 {
+			return nil, errors.New("x509: invalid private key length")
+		}
+		privKey.PrivateKey = privKey.PrivateKey[1:]
+	}
+	copy(privateKey[len(privateKey)-len(privKey.PrivateKey):], privKey.PrivateKey)
+	priv.X, priv.Y = curve.ScalarBaseMult(privateKey)
+	return priv, nil
+}
+
+func ParsePKCS8UnecryptedPrivateKey(der []byte) (*PrivateKey, error) {
+	var privKey pkcs8
+
+	if _, err := asn1.Unmarshal(der, &privKey); err != nil {
+		return nil, err
+	}
+	if !reflect.DeepEqual(privKey.Algo.Algorithm, oidSM2) {
+		return nil, errors.New("x509: not sm2 elliptic curve")
+	}
+	return ParseSm2PrivateKey(privKey.PrivateKey)
+}
+
+func ParsePKCS8EcryptedPrivateKey(der, pwd []byte) (*PrivateKey, error) {
+	var keyInfo EncryptedPrivateKeyInfo
+
+	_, err := asn1.Unmarshal(der, &keyInfo)
+	if err != nil {
+		return nil, errors.New("x509: unknown format")
+	}
+	if !reflect.DeepEqual(keyInfo.EncryptionAlgorithm.IdPBES2, oidPBES2) {
+		return nil, errors.New("x509: only support PBES2")
+	}
+	encryptionScheme := keyInfo.EncryptionAlgorithm.Pbes2Params.EncryptionScheme
+	keyDerivationFunc := keyInfo.EncryptionAlgorithm.Pbes2Params.KeyDerivationFunc
+	if !reflect.DeepEqual(keyDerivationFunc.IdPBKDF2, oidPBKDF2) {
+		return nil, errors.New("x509: only support PBKDF2")
+	}
+	pkdf2Params := keyDerivationFunc.Pkdf2Params
+	if !reflect.DeepEqual(encryptionScheme.EncryAlgo, oidAES128CBC) &&
+		!reflect.DeepEqual(encryptionScheme.EncryAlgo, oidAES256CBC) {
+		return nil, errors.New("x509: unknow encryption algorithm")
+	}
+	iv := encryptionScheme.IV
+	salt := pkdf2Params.Salt
+	iter := pkdf2Params.IterationCount
+	encryptedKey := keyInfo.EncryptedData
+	var key []byte
+	switch {
+	case pkdf2Params.Prf.Algorithm.Equal(oidKEYMD5):
+		key = pbkdf(pwd, salt, iter, 32, md5.New)
+		break
+	case pkdf2Params.Prf.Algorithm.Equal(oidKEYSHA1):
+		key = pbkdf(pwd, salt, iter, 32, sha1.New)
+		break
+	case pkdf2Params.Prf.Algorithm.Equal(oidKEYSHA256):
+		key = pbkdf(pwd, salt, iter, 32, sha256.New)
+		break
+	case pkdf2Params.Prf.Algorithm.Equal(oidKEYSHA512):
+		key = pbkdf(pwd, salt, iter, 32, sha512.New)
+		break
+	default:
+		return nil, errors.New("x509: unknown hash algorithm")
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	mode := cipher.NewCBCDecrypter(block, iv)
+	mode.CryptBlocks(encryptedKey, encryptedKey)
+	rKey, err := ParsePKCS8UnecryptedPrivateKey(encryptedKey)
+	if err != nil {
+		return nil, errors.New("pkcs8: incorrect password")
+	}
+	return rKey, nil
+}
+
+func ParsePKCS8PrivateKey(der, pwd []byte) (*PrivateKey, error) {
+	if pwd == nil {
+		return ParsePKCS8UnecryptedPrivateKey(der)
+	}
+	return ParsePKCS8EcryptedPrivateKey(der, pwd)
+}
+
+func MarshalSm2UnecryptedPrivateKey(key *PrivateKey) ([]byte, error) {
+	var r pkcs8
+	var priv sm2PrivateKey
+	var algo pkix.AlgorithmIdentifier
+
+	algo.Algorithm = oidSM2
+	algo.Parameters.Class = 0
+	algo.Parameters.Tag = 6
+	algo.Parameters.IsCompound = false
+	algo.Parameters.FullBytes = []byte{6, 8, 42, 129, 28, 207, 85, 1, 130, 45} // asn1.Marshal(asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 301})
+	priv.Version = 1
+	priv.NamedCurveOID = oidNamedCurveP256SM2
+	priv.PublicKey = asn1.BitString{Bytes: elliptic.Marshal(key.Curve, key.X, key.Y)}
+	priv.PrivateKey = key.D.Bytes()
+	r.Version = 0
+	r.Algo = algo
+	r.PrivateKey, _ = asn1.Marshal(priv)
+	return asn1.Marshal(r)
+}
+
+func MarshalSm2EcryptedPrivateKey(PrivKey *PrivateKey, pwd []byte) ([]byte, error) {
+	der, err := MarshalSm2UnecryptedPrivateKey(PrivKey)
+	if err != nil {
+		return nil, err
+	}
+	iter := 2048
+	salt := make([]byte, 8)
+	iv := make([]byte, 16)
+	rand.Reader.Read(salt)
+	rand.Reader.Read(iv)
+	key := pbkdf(pwd, salt, iter, 32, sha1.New) // 默认是SHA1
+	padding := aes.BlockSize - len(der)%aes.BlockSize
+	if padding > 0 {
+		n := len(der)
+		der = append(der, make([]byte, padding)...)
+		for i := 0; i < padding; i++ {
+			der[n+i] = byte(padding)
+		}
+	}
+	encryptedKey := make([]byte, len(der))
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	mode := cipher.NewCBCEncrypter(block, iv)
+	mode.CryptBlocks(encryptedKey, der)
+	var algorithmIdentifier pkix.AlgorithmIdentifier
+	algorithmIdentifier.Algorithm = oidKEYSHA1
+	algorithmIdentifier.Parameters.Tag = 5
+	algorithmIdentifier.Parameters.IsCompound = false
+	algorithmIdentifier.Parameters.FullBytes = []byte{5, 0}
+	keyDerivationFunc := Pbes2KDfs{
+		oidPBKDF2,
+		Pkdf2Params{
+			salt,
+			iter,
+			algorithmIdentifier,
+		},
+	}
+	encryptionScheme := Pbes2Encs{
+		oidAES256CBC,
+		iv,
+	}
+	pbes2Algorithms := Pbes2Algorithms{
+		oidPBES2,
+		Pbes2Params{
+			keyDerivationFunc,
+			encryptionScheme,
+		},
+	}
+	encryptedPkey := EncryptedPrivateKeyInfo{
+		pbes2Algorithms,
+		encryptedKey,
+	}
+	return asn1.Marshal(encryptedPkey)
+}
+
+func MarshalSm2PrivateKey(key *PrivateKey, pwd []byte) ([]byte, error) {
+	if pwd == nil {
+		return MarshalSm2UnecryptedPrivateKey(key)
+	}
+	return MarshalSm2EcryptedPrivateKey(key, pwd)
+}
+
+func ReadPrivateKeyFromMem(data []byte, pwd []byte) (*PrivateKey, error) {
+	var block *pem.Block
+
+	block, _ = pem.Decode(data)
+	if block == nil {
+		return nil, errors.New("failed to decode private key")
+	}
+	priv, err := ParsePKCS8PrivateKey(block.Bytes, pwd)
+	return priv, err
+}
+
+func ReadPrivateKeyFromPem(FileName string, pwd []byte) (*PrivateKey, error) {
+	data, err := ioutil.ReadFile(FileName)
+	if err != nil {
+		return nil, err
+	}
+	return ReadPrivateKeyFromMem(data, pwd)
+}
+
+func WritePrivateKeytoMem(key *PrivateKey, pwd []byte) ([]byte, error) {
+	var block *pem.Block
+
+	der, err := MarshalSm2PrivateKey(key, pwd)
+	if err != nil {
+		return nil, err
+	}
+	if pwd != nil {
+		block = &pem.Block{
+			Type:  "ENCRYPTED PRIVATE KEY",
+			Bytes: der,
+		}
+	} else {
+		block = &pem.Block{
+			Type:  "PRIVATE KEY",
+			Bytes: der,
+		}
+	}
+	return pem.EncodeToMemory(block), nil
+}
+
+func WritePrivateKeytoPem(FileName string, key *PrivateKey, pwd []byte) (bool, error) {
+	var block *pem.Block
+
+	der, err := MarshalSm2PrivateKey(key, pwd)
+	if err != nil {
+		return false, err
+	}
+	if pwd != nil {
+		block = &pem.Block{
+			Type:  "ENCRYPTED PRIVATE KEY",
+			Bytes: der,
+		}
+	} else {
+		block = &pem.Block{
+			Type:  "PRIVATE KEY",
+			Bytes: der,
+		}
+	}
+	file, err := os.Create(FileName)
+	if err != nil {
+		return false, err
+	}
+	defer file.Close()
+	err = pem.Encode(file, block)
+	if err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+func ReadPublicKeyFromMem(data []byte, _ []byte) (*PublicKey, error) {
+	block, _ := pem.Decode(data)
+	if block == nil || block.Type != "PUBLIC KEY" {
+		return nil, errors.New("failed to decode public key")
+	}
+	pub, err := ParseSm2PublicKey(block.Bytes)
+	return pub, err
+}
+
+func ReadPublicKeyFromPem(FileName string, pwd []byte) (*PublicKey, error) {
+	data, err := ioutil.ReadFile(FileName)
+	if err != nil {
+		return nil, err
+	}
+	return ReadPublicKeyFromMem(data, pwd)
+}
+
+func WritePublicKeytoMem(key *PublicKey, _ []byte) ([]byte, error) {
+	der, err := MarshalSm2PublicKey(key)
+	if err != nil {
+		return nil, err
+	}
+	block := &pem.Block{
+		Type:  "PUBLIC KEY",
+		Bytes: der,
+	}
+	return pem.EncodeToMemory(block), nil
+}
+
+func WritePublicKeytoPem(FileName string, key *PublicKey, _ []byte) (bool, error) {
+	der, err := MarshalSm2PublicKey(key)
+	if err != nil {
+		return false, err
+	}
+	block := &pem.Block{
+		Type:  "PUBLIC KEY",
+		Bytes: der,
+	}
+	file, err := os.Create(FileName)
+	defer file.Close()
+	if err != nil {
+		return false, err
+	}
+	err = pem.Encode(file, block)
+	if err != nil {
+		return false, err
+	}
+	return true, nil
+}
diff --git a/crypto/sm2/sm2.go b/crypto/sm2/sm2.go
new file mode 100644
index 00000000..897c1091
--- /dev/null
+++ b/crypto/sm2/sm2.go
@@ -0,0 +1,524 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sm2
+
+// reference to ecdsa
+import (
+	"bytes"
+	"crypto"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha512"
+	"encoding/asn1"
+	"encoding/binary"
+	"errors"
+	"io"
+	"math/big"
+
+	"github.com/bytom/crypto/sm3"
+)
+
+const (
+	aesIV = "IV for <SM2> CTR"
+)
+
+type PublicKey struct {
+	elliptic.Curve
+	X, Y *big.Int
+}
+
+type PrivateKey struct {
+	PublicKey
+	D *big.Int
+}
+
+type sm2Signature struct {
+	R, S *big.Int
+}
+
+// The SM2's private key contains the public key
+func (priv *PrivateKey) Public() crypto.PublicKey {
+	return &priv.PublicKey
+}
+
+func SignDigitToSignData(r, s *big.Int) ([]byte, error) {
+	return asn1.Marshal(sm2Signature{r, s})
+}
+
+func SignDataToSignDigit(sign []byte) (*big.Int, *big.Int, error) {
+	var sm2Sign sm2Signature
+
+	_, err := asn1.Unmarshal(sign, &sm2Sign)
+	if err != nil {
+		return nil, nil, err
+	}
+	return sm2Sign.R, sm2Sign.S, nil
+}
+
+// sign format = 30 + len(z) + 02 + len(r) + r + 02 + len(s) + s, z being what follows its size, ie 02+len(r)+r+02+len(s)+s
+func (priv *PrivateKey) Sign(rand io.Reader, msg []byte, opts crypto.SignerOpts) ([]byte, error) {
+	r, s, err := Sign(priv, msg)
+	if err != nil {
+		return nil, err
+	}
+	return asn1.Marshal(sm2Signature{r, s})
+}
+
+func (priv *PrivateKey) Decrypt(data []byte) ([]byte, error) {
+	return Decrypt(priv, data)
+}
+
+func (pub *PublicKey) Verify(msg []byte, sign []byte) bool {
+	var sm2Sign sm2Signature
+
+	_, err := asn1.Unmarshal(sign, &sm2Sign)
+	if err != nil {
+		return false
+	}
+	return Verify(pub, msg, sm2Sign.R, sm2Sign.S)
+}
+
+func (pub *PublicKey) Encrypt(data []byte) ([]byte, error) {
+	return Encrypt(pub, data)
+}
+
+var one = new(big.Int).SetInt64(1)
+
+func intToBytes(x int) []byte {
+	var buf = make([]byte, 4)
+
+	binary.BigEndian.PutUint32(buf, uint32(x))
+	return buf
+}
+
+func kdf(x, y []byte, length int) ([]byte, bool) {
+	var c []byte
+
+	ct := 1
+	h := sm3.New()
+	x = append(x, y...)
+	for i, j := 0, (length+31)/32; i < j; i++ {
+		h.Reset()
+		h.Write(x)
+		h.Write(intToBytes(ct))
+		hash := h.Sum(nil)
+		if i+1 == j && length%32 != 0 {
+			c = append(c, hash[:length%32]...)
+		} else {
+			c = append(c, hash...)
+		}
+		ct++
+	}
+	for i := 0; i < length; i++ {
+		if c[i] != 0 {
+			return c, true
+		}
+	}
+	return c, false
+}
+
+func randFieldElement(c elliptic.Curve, rand io.Reader) (k *big.Int, err error) {
+	params := c.Params()
+	b := make([]byte, params.BitSize/8+8)
+	_, err = io.ReadFull(rand, b)
+	if err != nil {
+		return
+	}
+	k = new(big.Int).SetBytes(b)
+	n := new(big.Int).Sub(params.N, one)
+	k.Mod(k, n)
+	k.Add(k, one)
+	return
+}
+
+func GenerateKey() (*PrivateKey, error) {
+	c := P256Sm2()
+	k, err := randFieldElement(c, rand.Reader)
+	if err != nil {
+		return nil, err
+	}
+	priv := new(PrivateKey)
+	priv.PublicKey.Curve = c
+	priv.D = k
+	priv.PublicKey.X, priv.PublicKey.Y = c.ScalarBaseMult(k.Bytes())
+	return priv, nil
+}
+
+var errZeroParam = errors.New("zero parameter")
+
+func Sign(priv *PrivateKey, hash []byte) (r, s *big.Int, err error) {
+	entropylen := (priv.Curve.Params().BitSize + 7) / 16
+	if entropylen > 32 {
+		entropylen = 32
+	}
+	entropy := make([]byte, entropylen)
+	_, err = io.ReadFull(rand.Reader, entropy)
+	if err != nil {
+		return
+	}
+
+	// Initialize an SHA-512 hash context; digest ...
+	md := sha512.New()
+	md.Write(priv.D.Bytes()) // the private key,
+	md.Write(entropy)        // the entropy,
+	md.Write(hash)           // and the input hash;
+	key := md.Sum(nil)[:32]  // and compute ChopMD-256(SHA-512),
+	// which is an indifferentiable MAC.
+
+	// Create an AES-CTR instance to use as a CSPRNG.
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Create a CSPRNG that xors a stream of zeros with
+	// the output of the AES-CTR instance.
+	csprng := cipher.StreamReader{
+		R: zeroReader,
+		S: cipher.NewCTR(block, []byte(aesIV)),
+	}
+
+	// See [NSA] 3.4.1
+	c := priv.PublicKey.Curve
+	N := c.Params().N
+	if N.Sign() == 0 {
+		return nil, nil, errZeroParam
+	}
+	var k *big.Int
+	e := new(big.Int).SetBytes(hash)
+	for { // 调整算法细节以实现SM2
+		for {
+			k, err = randFieldElement(c, csprng)
+			if err != nil {
+				r = nil
+				return
+			}
+			r, _ = priv.Curve.ScalarBaseMult(k.Bytes())
+			r.Add(r, e)
+			r.Mod(r, N)
+			if r.Sign() != 0 {
+				break
+			}
+			if t := new(big.Int).Add(r, k); t.Cmp(N) == 0 {
+				break
+			}
+		}
+		rD := new(big.Int).Mul(priv.D, r)
+		s = new(big.Int).Sub(k, rD)
+		d1 := new(big.Int).Add(priv.D, one)
+		d1Inv := new(big.Int).ModInverse(d1, N)
+		s.Mul(s, d1Inv)
+		s.Mod(s, N)
+		if s.Sign() != 0 {
+			break
+		}
+	}
+	return
+}
+
+func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool {
+	c := pub.Curve
+	N := c.Params().N
+
+	if r.Sign() <= 0 || s.Sign() <= 0 {
+		return false
+	}
+	if r.Cmp(N) >= 0 || s.Cmp(N) >= 0 {
+		return false
+	}
+
+	// 调整算法细节以实现SM2
+	t := new(big.Int).Add(r, s)
+	t.Mod(t, N)
+	if t.Sign() == 0 {
+		return false
+	}
+
+	var x *big.Int
+	x1, y1 := c.ScalarBaseMult(s.Bytes())
+	x2, y2 := c.ScalarMult(pub.X, pub.Y, t.Bytes())
+	x, _ = c.Add(x1, y1, x2, y2)
+
+	e := new(big.Int).SetBytes(hash)
+	x.Add(x, e)
+	x.Mod(x, N)
+	return x.Cmp(r) == 0
+}
+
+func Sm2Sign(priv *PrivateKey, msg, uid []byte) (r, s *big.Int, err error) {
+	za, err := ZA(&priv.PublicKey, uid)
+	if err != nil {
+		return nil, nil, err
+	}
+	e, err := msgHash(za, msg)
+	if err != nil {
+		return nil, nil, err
+	}
+	c := priv.PublicKey.Curve
+	N := c.Params().N
+	if N.Sign() == 0 {
+		return nil, nil, errZeroParam
+	}
+	var k *big.Int
+	for { // 调整算法细节以实现SM2
+		for {
+			k, err = randFieldElement(c, rand.Reader)
+			if err != nil {
+				r = nil
+				return
+			}
+			r, _ = priv.Curve.ScalarBaseMult(k.Bytes())
+			r.Add(r, e)
+			r.Mod(r, N)
+			if r.Sign() != 0 {
+				break
+			}
+			if t := new(big.Int).Add(r, k); t.Cmp(N) == 0 {
+				break
+			}
+		}
+		rD := new(big.Int).Mul(priv.D, r)
+		s = new(big.Int).Sub(k, rD)
+		d1 := new(big.Int).Add(priv.D, one)
+		d1Inv := new(big.Int).ModInverse(d1, N)
+		s.Mul(s, d1Inv)
+		s.Mod(s, N)
+		if s.Sign() != 0 {
+			break
+		}
+	}
+	return
+}
+
+func Sm2Verify(pub *PublicKey, msg, uid []byte, r, s *big.Int) bool {
+	c := pub.Curve
+	N := c.Params().N
+	one := new(big.Int).SetInt64(1)
+	if r.Cmp(one) < 0 || s.Cmp(one) < 0 {
+		return false
+	}
+	if r.Cmp(N) >= 0 || s.Cmp(N) >= 0 {
+		return false
+	}
+	za, err := ZA(pub, uid)
+	if err != nil {
+		return false
+	}
+	e, err := msgHash(za, msg)
+	if err != nil {
+		return false
+	}
+	t := new(big.Int).Add(r, s)
+	t.Mod(t, N)
+	if t.Sign() == 0 {
+		return false
+	}
+	var x *big.Int
+	x1, y1 := c.ScalarBaseMult(s.Bytes())
+	x2, y2 := c.ScalarMult(pub.X, pub.Y, t.Bytes())
+	x, _ = c.Add(x1, y1, x2, y2)
+
+	x.Add(x, e)
+	x.Mod(x, N)
+	return x.Cmp(r) == 0
+}
+
+func msgHash(za, msg []byte) (*big.Int, error) {
+	e := sm3.New()
+	e.Write(za)
+	e.Write(msg)
+	return new(big.Int).SetBytes(e.Sum(nil)[:32]), nil
+}
+
+// ZA = H256(ENTLA || IDA || a || b || xG || yG || xA || yA)
+func ZA(pub *PublicKey, uid []byte) ([]byte, error) {
+	za := sm3.New()
+	uidLen := len(uid)
+	if uidLen >= 8192 {
+		return []byte{}, errors.New("SM2: uid too large")
+	}
+	Entla := uint16(8 * uidLen)
+	za.Write([]byte{byte((Entla >> 8) & 0xFF)})
+	za.Write([]byte{byte(Entla & 0xFF)})
+	za.Write(uid)
+	za.Write(sm2P256ToBig(&sm2P256.a).Bytes())
+	za.Write(sm2P256.B.Bytes())
+	za.Write(sm2P256.Gx.Bytes())
+	za.Write(sm2P256.Gy.Bytes())
+
+	xBuf := pub.X.Bytes()
+	yBuf := pub.Y.Bytes()
+	if n := len(xBuf); n < 32 {
+		xBuf = append(zeroByteSlice[:32-n], xBuf...)
+	}
+	za.Write(xBuf)
+	za.Write(yBuf)
+	return za.Sum(nil)[:32], nil
+}
+
+// 32byte
+var zeroByteSlice = []byte{
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+}
+
+/*
+ * sm2密文结构如下:
+ *  x
+ *  y
+ *  hash
+ *  CipherText
+ */
+func Encrypt(pub *PublicKey, data []byte) ([]byte, error) {
+	length := len(data)
+	for {
+		c := []byte{}
+		curve := pub.Curve
+		k, err := randFieldElement(curve, rand.Reader)
+		if err != nil {
+			return nil, err
+		}
+		x1, y1 := curve.ScalarBaseMult(k.Bytes())
+		x2, y2 := curve.ScalarMult(pub.X, pub.Y, k.Bytes())
+		x1Buf := x1.Bytes()
+		y1Buf := y1.Bytes()
+		x2Buf := x2.Bytes()
+		y2Buf := y2.Bytes()
+		if n := len(x1Buf); n < 32 {
+			x1Buf = append(zeroByteSlice[:32-n], x1Buf...)
+		}
+		if n := len(y1Buf); n < 32 {
+			y1Buf = append(zeroByteSlice[:32-n], y1Buf...)
+		}
+		if n := len(x2Buf); n < 32 {
+			x2Buf = append(zeroByteSlice[:32-n], x2Buf...)
+		}
+		if n := len(y2Buf); n < 32 {
+			y2Buf = append(zeroByteSlice[:32-n], y2Buf...)
+		}
+		c = append(c, x1Buf...) // x分量
+		c = append(c, y1Buf...) // y分量
+		tm := []byte{}
+		tm = append(tm, x2Buf...)
+		tm = append(tm, data...)
+		tm = append(tm, y2Buf...)
+		h := sm3.Sm3Sum(tm)
+		c = append(c, h...)
+		ct, ok := kdf(x2Buf, y2Buf, length) // 密文
+		if !ok {
+			continue
+		}
+		c = append(c, ct...)
+		for i := 0; i < length; i++ {
+			c[96+i] ^= data[i]
+		}
+		return append([]byte{0x04}, c...), nil
+	}
+}
+
+func Decrypt(priv *PrivateKey, data []byte) ([]byte, error) {
+	data = data[1:]
+	length := len(data) - 96
+	curve := priv.Curve
+	x := new(big.Int).SetBytes(data[:32])
+	y := new(big.Int).SetBytes(data[32:64])
+	x2, y2 := curve.ScalarMult(x, y, priv.D.Bytes())
+	x2Buf := x2.Bytes()
+	y2Buf := y2.Bytes()
+	if n := len(x2Buf); n < 32 {
+		x2Buf = append(zeroByteSlice[:32-n], x2Buf...)
+	}
+	if n := len(y2Buf); n < 32 {
+		y2Buf = append(zeroByteSlice[:32-n], y2Buf...)
+	}
+	c, ok := kdf(x2Buf, y2Buf, length)
+	if !ok {
+		return nil, errors.New("Decrypt: failed to decrypt")
+	}
+	for i := 0; i < length; i++ {
+		c[i] ^= data[i+96]
+	}
+	tm := []byte{}
+	tm = append(tm, x2Buf...)
+	tm = append(tm, c...)
+	tm = append(tm, y2Buf...)
+	h := sm3.Sm3Sum(tm)
+	if bytes.Compare(h, data[64:96]) != 0 {
+		return c, errors.New("Decrypt: failed to decrypt")
+	}
+	return c, nil
+}
+
+type zr struct {
+	io.Reader
+}
+
+func (z *zr) Read(dst []byte) (n int, err error) {
+	for i := range dst {
+		dst[i] = 0
+	}
+	return len(dst), nil
+}
+
+var zeroReader = &zr{}
+
+func getLastBit(a *big.Int) uint {
+	return a.Bit(0)
+}
+
+func Compress(a *PublicKey) []byte {
+	buf := []byte{}
+	yp := getLastBit(a.Y)
+	buf = append(buf, a.X.Bytes()...)
+	if n := len(a.X.Bytes()); n < 32 {
+		buf = append(zeroByteSlice[:(32-n)], buf...)
+	}
+	buf = append([]byte{byte(yp)}, buf...)
+	return buf
+}
+
+func Decompress(a []byte) *PublicKey {
+	var aa, xx, xx3 sm2P256FieldElement
+
+	P256Sm2()
+	x := new(big.Int).SetBytes(a[1:])
+	curve := sm2P256
+	sm2P256FromBig(&xx, x)
+	sm2P256Square(&xx3, &xx)       // x3 = x ^ 2
+	sm2P256Mul(&xx3, &xx3, &xx)    // x3 = x ^ 2 * x
+	sm2P256Mul(&aa, &curve.a, &xx) // a = a * x
+	sm2P256Add(&xx3, &xx3, &aa)
+	sm2P256Add(&xx3, &xx3, &curve.b)
+
+	y2 := sm2P256ToBig(&xx3)
+	y := new(big.Int).ModSqrt(y2, sm2P256.P)
+	if getLastBit(y) != uint(a[0]) {
+		y.Sub(sm2P256.P, y)
+	}
+	return &PublicKey{
+		Curve: P256Sm2(),
+		X:     x,
+		Y:     y,
+	}
+}
diff --git a/crypto/sm2/sm2_test.go b/crypto/sm2/sm2_test.go
new file mode 100644
index 00000000..0820118a
--- /dev/null
+++ b/crypto/sm2/sm2_test.go
@@ -0,0 +1,219 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+                 http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sm2
+
+import (
+	"crypto/rand"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/big"
+	"net"
+	"os"
+	"testing"
+	"time"
+)
+
+func TestSm2(t *testing.T) {
+	priv, err := GenerateKey() // 生成密钥对
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%v\n", priv.Curve.IsOnCurve(priv.X, priv.Y)) // 验证是否为sm2的曲线
+	pub := &priv.PublicKey
+	msg := []byte("123456")
+	d0, err := pub.Encrypt(msg)
+	if err != nil {
+		fmt.Printf("Error: failed to encrypt %s: %v\n", msg, err)
+		return
+	}
+	fmt.Printf("Cipher text = %v\n", d0)
+	d1, err := priv.Decrypt(d0)
+	if err != nil {
+		fmt.Printf("Error: failed to decrypt: %v\n", err)
+	}
+	fmt.Printf("clear text = %s\n", d1)
+	ok, err := WritePrivateKeytoPem("priv.pem", priv, nil) // 生成密钥文件
+	if ok != true {
+		log.Fatal(err)
+	}
+	pubKey, _ := priv.Public().(*PublicKey)
+	ok, err = WritePublicKeytoPem("pub.pem", pubKey, nil) // 生成公钥文件
+	if ok != true {
+		log.Fatal(err)
+	}
+	msg = []byte("test")
+	err = ioutil.WriteFile("ifile", msg, os.FileMode(0644)) // 生成测试文件
+	if err != nil {
+		log.Fatal(err)
+	}
+	privKey, err := ReadPrivateKeyFromPem("priv.pem", nil) // 读取密钥
+	if err != nil {
+		log.Fatal(err)
+	}
+	pubKey, err = ReadPublicKeyFromPem("pub.pem", nil) // 读取公钥
+	if err != nil {
+		log.Fatal(err)
+	}
+	msg, _ = ioutil.ReadFile("ifile")                // 从文件读取数据
+	sign, err := privKey.Sign(rand.Reader, msg, nil) // 签名
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = ioutil.WriteFile("ofile", sign, os.FileMode(0644))
+	if err != nil {
+		log.Fatal(err)
+	}
+	signdata, _ := ioutil.ReadFile("ofile")
+	ok = privKey.Verify(msg, signdata) // 密钥验证
+	if ok != true {
+		fmt.Printf("Verify error\n")
+	} else {
+		fmt.Printf("Verify ok\n")
+	}
+	ok = pubKey.Verify(msg, signdata) // 公钥验证
+	if ok != true {
+		fmt.Printf("Verify error\n")
+	} else {
+		fmt.Printf("Verify ok\n")
+	}
+	templateReq := CertificateRequest{
+		Subject: pkix.Name{
+			CommonName:   "test.example.com",
+			Organization: []string{"Test"},
+		},
+		//		SignatureAlgorithm: ECDSAWithSHA256,
+		SignatureAlgorithm: SM2WithSM3,
+	}
+	_, err = CreateCertificateRequestToPem("req.pem", &templateReq, privKey)
+	if err != nil {
+		log.Fatal(err)
+	}
+	req, err := ReadCertificateRequestFromPem("req.pem")
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = req.CheckSignature()
+	if err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Printf("CheckSignature ok\n")
+	}
+	testExtKeyUsage := []ExtKeyUsage{ExtKeyUsageClientAuth, ExtKeyUsageServerAuth}
+	testUnknownExtKeyUsage := []asn1.ObjectIdentifier{[]int{1, 2, 3}, []int{2, 59, 1}}
+	extraExtensionData := []byte("extra extension")
+	commonName := "test.example.com"
+	template := Certificate{
+		// SerialNumber is negative to ensure that negative
+		// values are parsed. This is due to the prevalence of
+		// buggy code that produces certificates with negative
+		// serial numbers.
+		SerialNumber: big.NewInt(-1),
+		Subject: pkix.Name{
+			CommonName:   commonName,
+			Organization: []string{"TEST"},
+			Country:      []string{"China"},
+			ExtraNames: []pkix.AttributeTypeAndValue{
+				{
+					Type:  []int{2, 5, 4, 42},
+					Value: "Gopher",
+				},
+				// This should override the Country, above.
+				{
+					Type:  []int{2, 5, 4, 6},
+					Value: "NL",
+				},
+			},
+		},
+		NotBefore: time.Unix(1000, 0),
+		NotAfter:  time.Unix(100000, 0),
+
+		//		SignatureAlgorithm: ECDSAWithSHA256,
+		SignatureAlgorithm: SM2WithSM3,
+
+		SubjectKeyId: []byte{1, 2, 3, 4},
+		KeyUsage:     KeyUsageCertSign,
+
+		ExtKeyUsage:        testExtKeyUsage,
+		UnknownExtKeyUsage: testUnknownExtKeyUsage,
+
+		BasicConstraintsValid: true,
+		IsCA: true,
+
+		OCSPServer:            []string{"http://ocsp.example.com"},
+		IssuingCertificateURL: []string{"http://crt.example.com/ca1.crt"},
+
+		DNSNames:       []string{"test.example.com"},
+		EmailAddresses: []string{"gopher@golang.org"},
+		IPAddresses:    []net.IP{net.IPv4(127, 0, 0, 1).To4(), net.ParseIP("2001:4860:0:2001::68")},
+
+		PolicyIdentifiers:   []asn1.ObjectIdentifier{[]int{1, 2, 3}},
+		PermittedDNSDomains: []string{".example.com", "example.com"},
+
+		CRLDistributionPoints: []string{"http://crl1.example.com/ca1.crl", "http://crl2.example.com/ca1.crl"},
+
+		ExtraExtensions: []pkix.Extension{
+			{
+				Id:    []int{1, 2, 3, 4},
+				Value: extraExtensionData,
+			},
+			// This extension should override the SubjectKeyId, above.
+			{
+				Id:       oidExtensionSubjectKeyId,
+				Critical: false,
+				Value:    []byte{0x04, 0x04, 4, 3, 2, 1},
+			},
+		},
+	}
+	pubKey, _ = priv.Public().(*PublicKey)
+	ok, _ = CreateCertificateToPem("cert.pem", &template, &template, pubKey, privKey)
+	if ok != true {
+		fmt.Printf("failed to create cert file\n")
+	}
+	cert, err := ReadCertificateFromPem("cert.pem")
+	if err != nil {
+		fmt.Printf("failed to read cert file")
+	}
+	err = cert.CheckSignature(cert.SignatureAlgorithm, cert.RawTBSCertificate, cert.Signature)
+	if err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Printf("CheckSignature ok\n")
+	}
+}
+
+func BenchmarkSM2(t *testing.B) {
+	t.ReportAllocs()
+	for i := 0; i < t.N; i++ {
+		priv, err := GenerateKey() // 生成密钥对
+		if err != nil {
+			log.Fatal(err)
+		}
+		msg := []byte("test")
+		sign, err := priv.Sign(rand.Reader, msg, nil) // 签名
+		if err != nil {
+			log.Fatal(err)
+		}
+		ok := priv.Verify(msg, sign) // 密钥验证
+		if ok != true {
+			fmt.Printf("Verify error\n")
+		} else {
+			fmt.Printf("Verify ok\n")
+		}
+	}
+}
diff --git a/crypto/sm2/verify.go b/crypto/sm2/verify.go
new file mode 100644
index 00000000..e822b22b
--- /dev/null
+++ b/crypto/sm2/verify.go
@@ -0,0 +1,568 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sm2
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"net"
+	"runtime"
+	"strings"
+	"time"
+	"unicode/utf8"
+)
+
+type InvalidReason int
+
+const (
+	// NotAuthorizedToSign results when a certificate is signed by another
+	// which isn't marked as a CA certificate.
+	NotAuthorizedToSign InvalidReason = iota
+	// Expired results when a certificate has expired, based on the time
+	// given in the VerifyOptions.
+	Expired
+	// CANotAuthorizedForThisName results when an intermediate or root
+	// certificate has a name constraint which doesn't include the name
+	// being checked.
+	CANotAuthorizedForThisName
+	// TooManyIntermediates results when a path length constraint is
+	// violated.
+	TooManyIntermediates
+	// IncompatibleUsage results when the certificate's key usage indicates
+	// that it may only be used for a different purpose.
+	IncompatibleUsage
+	// NameMismatch results when the subject name of a parent certificate
+	// does not match the issuer name in the child.
+	NameMismatch
+)
+
+// CertificateInvalidError results when an odd error occurs. Users of this
+// library probably want to handle all these errors uniformly.
+type CertificateInvalidError struct {
+	Cert   *Certificate
+	Reason InvalidReason
+}
+
+func (e CertificateInvalidError) Error() string {
+	switch e.Reason {
+	case NotAuthorizedToSign:
+		return "x509: certificate is not authorized to sign other certificates"
+	case Expired:
+		return "x509: certificate has expired or is not yet valid"
+	case CANotAuthorizedForThisName:
+		return "x509: a root or intermediate certificate is not authorized to sign in this domain"
+	case TooManyIntermediates:
+		return "x509: too many intermediates for path length constraint"
+	case IncompatibleUsage:
+		return "x509: certificate specifies an incompatible key usage"
+	case NameMismatch:
+		return "x509: issuer name does not match subject from issuing certificate"
+	}
+	return "x509: unknown error"
+}
+
+// HostnameError results when the set of authorized names doesn't match the
+// requested name.
+type HostnameError struct {
+	Certificate *Certificate
+	Host        string
+}
+
+func (h HostnameError) Error() string {
+	c := h.Certificate
+
+	var valid string
+	if ip := net.ParseIP(h.Host); ip != nil {
+		// Trying to validate an IP
+		if len(c.IPAddresses) == 0 {
+			return "x509: cannot validate certificate for " + h.Host + " because it doesn't contain any IP SANs"
+		}
+		for _, san := range c.IPAddresses {
+			if len(valid) > 0 {
+				valid += ", "
+			}
+			valid += san.String()
+		}
+	} else {
+		if len(c.DNSNames) > 0 {
+			valid = strings.Join(c.DNSNames, ", ")
+		} else {
+			valid = c.Subject.CommonName
+		}
+	}
+
+	if len(valid) == 0 {
+		return "x509: certificate is not valid for any names, but wanted to match " + h.Host
+	}
+	return "x509: certificate is valid for " + valid + ", not " + h.Host
+}
+
+// UnknownAuthorityError results when the certificate issuer is unknown
+type UnknownAuthorityError struct {
+	Cert *Certificate
+	// hintErr contains an error that may be helpful in determining why an
+	// authority wasn't found.
+	hintErr error
+	// hintCert contains a possible authority certificate that was rejected
+	// because of the error in hintErr.
+	hintCert *Certificate
+}
+
+func (e UnknownAuthorityError) Error() string {
+	s := "x509: certificate signed by unknown authority"
+	if e.hintErr != nil {
+		certName := e.hintCert.Subject.CommonName
+		if len(certName) == 0 {
+			if len(e.hintCert.Subject.Organization) > 0 {
+				certName = e.hintCert.Subject.Organization[0]
+			} else {
+				certName = "serial:" + e.hintCert.SerialNumber.String()
+			}
+		}
+		s += fmt.Sprintf(" (possibly because of %q while trying to verify candidate authority certificate %q)", e.hintErr, certName)
+	}
+	return s
+}
+
+// SystemRootsError results when we fail to load the system root certificates.
+type SystemRootsError struct {
+	Err error
+}
+
+func (se SystemRootsError) Error() string {
+	msg := "x509: failed to load system roots and no roots provided"
+	if se.Err != nil {
+		return msg + "; " + se.Err.Error()
+	}
+	return msg
+}
+
+// errNotParsed is returned when a certificate without ASN.1 contents is
+// verified. Platform-specific verification needs the ASN.1 contents.
+var errNotParsed = errors.New("x509: missing ASN.1 contents; use ParseCertificate")
+
+// VerifyOptions contains parameters for Certificate.Verify. It's a structure
+// because other PKIX verification APIs have ended up needing many options.
+type VerifyOptions struct {
+	DNSName       string
+	Intermediates *CertPool
+	Roots         *CertPool // if nil, the system roots are used
+	CurrentTime   time.Time // if zero, the current time is used
+	// KeyUsage specifies which Extended Key Usage values are acceptable.
+	// An empty list means ExtKeyUsageServerAuth. Key usage is considered a
+	// constraint down the chain which mirrors Windows CryptoAPI behavior,
+	// but not the spec. To accept any key usage, include ExtKeyUsageAny.
+	KeyUsages []ExtKeyUsage
+}
+
+const (
+	leafCertificate = iota
+	intermediateCertificate
+	rootCertificate
+)
+
+func matchNameConstraint(domain, constraint string) bool {
+	// The meaning of zero length constraints is not specified, but this
+	// code follows NSS and accepts them as valid for everything.
+	if len(constraint) == 0 {
+		return true
+	}
+
+	if len(domain) < len(constraint) {
+		return false
+	}
+
+	prefixLen := len(domain) - len(constraint)
+	if !strings.EqualFold(domain[prefixLen:], constraint) {
+		return false
+	}
+
+	if prefixLen == 0 {
+		return true
+	}
+
+	isSubdomain := domain[prefixLen-1] == '.'
+	constraintHasLeadingDot := constraint[0] == '.'
+	return isSubdomain != constraintHasLeadingDot
+}
+
+// isValid performs validity checks on the c.
+func (c *Certificate) isValid(certType int, currentChain []*Certificate, opts *VerifyOptions) error {
+	if len(currentChain) > 0 {
+		child := currentChain[len(currentChain)-1]
+		if !bytes.Equal(child.RawIssuer, c.RawSubject) {
+			return CertificateInvalidError{c, NameMismatch}
+		}
+	}
+	now := opts.CurrentTime
+	if now.IsZero() {
+		now = time.Now()
+	}
+	if now.Before(c.NotBefore) || now.After(c.NotAfter) {
+		return CertificateInvalidError{c, Expired}
+	}
+	if len(c.PermittedDNSDomains) > 0 {
+		ok := false
+		for _, constraint := range c.PermittedDNSDomains {
+			ok = matchNameConstraint(opts.DNSName, constraint)
+			if ok {
+				break
+			}
+		}
+
+		if !ok {
+			return CertificateInvalidError{c, CANotAuthorizedForThisName}
+		}
+	}
+
+	// KeyUsage status flags are ignored. From Engineering Security, Peter
+	// Gutmann: A European government CA marked its signing certificates as
+	// being valid for encryption only, but no-one noticed. Another
+	// European CA marked its signature keys as not being valid for
+	// signatures. A different CA marked its own trusted root certificate
+	// as being invalid for certificate signing. Another national CA
+	// distributed a certificate to be used to encrypt data for the
+	// country’s tax authority that was marked as only being usable for
+	// digital signatures but not for encryption. Yet another CA reversed
+	// the order of the bit flags in the keyUsage due to confusion over
+	// encoding endianness, essentially setting a random keyUsage in
+	// certificates that it issued. Another CA created a self-invalidating
+	// certificate by adding a certificate policy statement stipulating
+	// that the certificate had to be used strictly as specified in the
+	// keyUsage, and a keyUsage containing a flag indicating that the RSA
+	// encryption key could only be used for Diffie-Hellman key agreement.
+
+	if certType == intermediateCertificate && (!c.BasicConstraintsValid || !c.IsCA) {
+		return CertificateInvalidError{c, NotAuthorizedToSign}
+	}
+
+	if c.BasicConstraintsValid && c.MaxPathLen >= 0 {
+		numIntermediates := len(currentChain) - 1
+		if numIntermediates > c.MaxPathLen {
+			return CertificateInvalidError{c, TooManyIntermediates}
+		}
+	}
+
+	return nil
+}
+
+// Verify attempts to verify c by building one or more chains from c to a
+// certificate in opts.Roots, using certificates in opts.Intermediates if
+// needed. If successful, it returns one or more chains where the first
+// element of the chain is c and the last element is from opts.Roots.
+//
+// If opts.Roots is nil and system roots are unavailable the returned error
+// will be of type SystemRootsError.
+//
+// WARNING: this doesn't do any revocation checking.
+func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err error) {
+	// Platform-specific verification needs the ASN.1 contents so
+	// this makes the behavior consistent across platforms.
+	if len(c.Raw) == 0 {
+		return nil, errNotParsed
+	}
+	if opts.Intermediates != nil {
+		for _, intermediate := range opts.Intermediates.certs {
+			if len(intermediate.Raw) == 0 {
+				return nil, errNotParsed
+			}
+		}
+	}
+
+	// Use Windows's own verification and chain building.
+	if opts.Roots == nil && runtime.GOOS == "windows" {
+		return c.systemVerify(&opts)
+	}
+
+	if len(c.UnhandledCriticalExtensions) > 0 {
+		return nil, UnhandledCriticalExtension{}
+	}
+
+	if opts.Roots == nil {
+		opts.Roots = systemRootsPool()
+		if opts.Roots == nil {
+			return nil, SystemRootsError{systemRootsErr}
+		}
+	}
+
+	err = c.isValid(leafCertificate, nil, &opts)
+	if err != nil {
+		return
+	}
+
+	if len(opts.DNSName) > 0 {
+		err = c.VerifyHostname(opts.DNSName)
+		if err != nil {
+			return
+		}
+	}
+
+	var candidateChains [][]*Certificate
+	if opts.Roots.contains(c) {
+		candidateChains = append(candidateChains, []*Certificate{c})
+	} else {
+		if candidateChains, err = c.buildChains(make(map[int][][]*Certificate), []*Certificate{c}, &opts); err != nil {
+			return nil, err
+		}
+	}
+
+	keyUsages := opts.KeyUsages
+	if len(keyUsages) == 0 {
+		keyUsages = []ExtKeyUsage{ExtKeyUsageServerAuth}
+	}
+
+	// If any key usage is acceptable then we're done.
+	for _, usage := range keyUsages {
+		if usage == ExtKeyUsageAny {
+			chains = candidateChains
+			return
+		}
+	}
+
+	for _, candidate := range candidateChains {
+		if checkChainForKeyUsage(candidate, keyUsages) {
+			chains = append(chains, candidate)
+		}
+	}
+
+	if len(chains) == 0 {
+		err = CertificateInvalidError{c, IncompatibleUsage}
+	}
+
+	return
+}
+
+func appendToFreshChain(chain []*Certificate, cert *Certificate) []*Certificate {
+	n := make([]*Certificate, len(chain)+1)
+	copy(n, chain)
+	n[len(chain)] = cert
+	return n
+}
+
+func (c *Certificate) buildChains(cache map[int][][]*Certificate, currentChain []*Certificate, opts *VerifyOptions) (chains [][]*Certificate, err error) {
+	possibleRoots, failedRoot, rootErr := opts.Roots.findVerifiedParents(c)
+nextRoot:
+	for _, rootNum := range possibleRoots {
+		root := opts.Roots.certs[rootNum]
+
+		for _, cert := range currentChain {
+			if cert.Equal(root) {
+				continue nextRoot
+			}
+		}
+
+		err = root.isValid(rootCertificate, currentChain, opts)
+		if err != nil {
+			continue
+		}
+		chains = append(chains, appendToFreshChain(currentChain, root))
+	}
+
+	possibleIntermediates, failedIntermediate, intermediateErr := opts.Intermediates.findVerifiedParents(c)
+nextIntermediate:
+	for _, intermediateNum := range possibleIntermediates {
+		intermediate := opts.Intermediates.certs[intermediateNum]
+		for _, cert := range currentChain {
+			if cert.Equal(intermediate) {
+				continue nextIntermediate
+			}
+		}
+		err = intermediate.isValid(intermediateCertificate, currentChain, opts)
+		if err != nil {
+			continue
+		}
+		var childChains [][]*Certificate
+		childChains, ok := cache[intermediateNum]
+		if !ok {
+			childChains, err = intermediate.buildChains(cache, appendToFreshChain(currentChain, intermediate), opts)
+			cache[intermediateNum] = childChains
+		}
+		chains = append(chains, childChains...)
+	}
+
+	if len(chains) > 0 {
+		err = nil
+	}
+
+	if len(chains) == 0 && err == nil {
+		hintErr := rootErr
+		hintCert := failedRoot
+		if hintErr == nil {
+			hintErr = intermediateErr
+			hintCert = failedIntermediate
+		}
+		err = UnknownAuthorityError{c, hintErr, hintCert}
+	}
+
+	return
+}
+
+func matchHostnames(pattern, host string) bool {
+	host = strings.TrimSuffix(host, ".")
+	pattern = strings.TrimSuffix(pattern, ".")
+
+	if len(pattern) == 0 || len(host) == 0 {
+		return false
+	}
+
+	patternParts := strings.Split(pattern, ".")
+	hostParts := strings.Split(host, ".")
+
+	if len(patternParts) != len(hostParts) {
+		return false
+	}
+
+	for i, patternPart := range patternParts {
+		if i == 0 && patternPart == "*" {
+			continue
+		}
+		if patternPart != hostParts[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
+// toLowerCaseASCII returns a lower-case version of in. See RFC 6125 6.4.1. We use
+// an explicitly ASCII function to avoid any sharp corners resulting from
+// performing Unicode operations on DNS labels.
+func toLowerCaseASCII(in string) string {
+	// If the string is already lower-case then there's nothing to do.
+	isAlreadyLowerCase := true
+	for _, c := range in {
+		if c == utf8.RuneError {
+			// If we get a UTF-8 error then there might be
+			// upper-case ASCII bytes in the invalid sequence.
+			isAlreadyLowerCase = false
+			break
+		}
+		if 'A' <= c && c <= 'Z' {
+			isAlreadyLowerCase = false
+			break
+		}
+	}
+
+	if isAlreadyLowerCase {
+		return in
+	}
+
+	out := []byte(in)
+	for i, c := range out {
+		if 'A' <= c && c <= 'Z' {
+			out[i] += 'a' - 'A'
+		}
+	}
+	return string(out)
+}
+
+// VerifyHostname returns nil if c is a valid certificate for the named host.
+// Otherwise it returns an error describing the mismatch.
+func (c *Certificate) VerifyHostname(h string) error {
+	// IP addresses may be written in [ ].
+	candidateIP := h
+	if len(h) >= 3 && h[0] == '[' && h[len(h)-1] == ']' {
+		candidateIP = h[1 : len(h)-1]
+	}
+	if ip := net.ParseIP(candidateIP); ip != nil {
+		// We only match IP addresses against IP SANs.
+		// https://tools.ietf.org/html/rfc6125#appendix-B.2
+		for _, candidate := range c.IPAddresses {
+			if ip.Equal(candidate) {
+				return nil
+			}
+		}
+		return HostnameError{c, candidateIP}
+	}
+
+	lowered := toLowerCaseASCII(h)
+
+	if len(c.DNSNames) > 0 {
+		for _, match := range c.DNSNames {
+			if matchHostnames(toLowerCaseASCII(match), lowered) {
+				return nil
+			}
+		}
+		// If Subject Alt Name is given, we ignore the common name.
+	} else if matchHostnames(toLowerCaseASCII(c.Subject.CommonName), lowered) {
+		return nil
+	}
+
+	return HostnameError{c, h}
+}
+
+func checkChainForKeyUsage(chain []*Certificate, keyUsages []ExtKeyUsage) bool {
+	usages := make([]ExtKeyUsage, len(keyUsages))
+	copy(usages, keyUsages)
+
+	if len(chain) == 0 {
+		return false
+	}
+
+	usagesRemaining := len(usages)
+
+	// We walk down the list and cross out any usages that aren't supported
+	// by each certificate. If we cross out all the usages, then the chain
+	// is unacceptable.
+
+NextCert:
+	for i := len(chain) - 1; i >= 0; i-- {
+		cert := chain[i]
+		if len(cert.ExtKeyUsage) == 0 && len(cert.UnknownExtKeyUsage) == 0 {
+			// The certificate doesn't have any extended key usage specified.
+			continue
+		}
+
+		for _, usage := range cert.ExtKeyUsage {
+			if usage == ExtKeyUsageAny {
+				// The certificate is explicitly good for any usage.
+				continue NextCert
+			}
+		}
+
+		const invalidUsage ExtKeyUsage = -1
+
+	NextRequestedUsage:
+		for i, requestedUsage := range usages {
+			if requestedUsage == invalidUsage {
+				continue
+			}
+
+			for _, usage := range cert.ExtKeyUsage {
+				if requestedUsage == usage {
+					continue NextRequestedUsage
+				} else if requestedUsage == ExtKeyUsageServerAuth &&
+					(usage == ExtKeyUsageNetscapeServerGatedCrypto ||
+						usage == ExtKeyUsageMicrosoftServerGatedCrypto) {
+					// In order to support COMODO
+					// certificate chains, we have to
+					// accept Netscape or Microsoft SGC
+					// usages as equal to ServerAuth.
+					continue NextRequestedUsage
+				}
+			}
+
+			usages[i] = invalidUsage
+			usagesRemaining--
+			if usagesRemaining == 0 {
+				return false
+			}
+		}
+	}
+
+	return true
+}
diff --git a/crypto/sm2/x509.go b/crypto/sm2/x509.go
new file mode 100644
index 00000000..855e3b13
--- /dev/null
+++ b/crypto/sm2/x509.go
@@ -0,0 +1,2527 @@
+/*
+Copyright Suzhou Tongji Fintech Research Institute 2017 All Rights Reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// crypto/x509 add sm2 support
+package sm2
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/md5"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"hash"
+	"io"
+	"io/ioutil"
+	"math/big"
+	"net"
+	"os"
+	"strconv"
+	"time"
+
+	"golang.org/x/crypto/ripemd160"
+	"golang.org/x/crypto/sha3"
+
+	"github.com/bytom/crypto/sm3"
+)
+
+// pkixPublicKey reflects a PKIX public key structure. See SubjectPublicKeyInfo
+// in RFC 3280.
+type pkixPublicKey struct {
+	Algo      pkix.AlgorithmIdentifier
+	BitString asn1.BitString
+}
+
+// ParsePKIXPublicKey parses a DER encoded public key. These values are
+// typically found in PEM blocks with "BEGIN PUBLIC KEY".
+//
+// Supported key types include RSA, DSA, and ECDSA. Unknown key
+// types result in an error.
+//
+// On success, pub will be of type *rsa.PublicKey, *dsa.PublicKey,
+// or *ecdsa.PublicKey.
+func ParsePKIXPublicKey(derBytes []byte) (pub interface{}, err error) {
+	var pki publicKeyInfo
+
+	if rest, err := asn1.Unmarshal(derBytes, &pki); err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after ASN.1 of public-key")
+	}
+	algo := getPublicKeyAlgorithmFromOID(pki.Algorithm.Algorithm)
+	if algo == UnknownPublicKeyAlgorithm {
+		return nil, errors.New("x509: unknown public key algorithm")
+	}
+	return parsePublicKey(algo, &pki)
+}
+
+func marshalPublicKey(pub interface{}) (publicKeyBytes []byte, publicKeyAlgorithm pkix.AlgorithmIdentifier, err error) {
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		publicKeyBytes, err = asn1.Marshal(rsaPublicKey{
+			N: pub.N,
+			E: pub.E,
+		})
+		if err != nil {
+			return nil, pkix.AlgorithmIdentifier{}, err
+		}
+		publicKeyAlgorithm.Algorithm = oidPublicKeyRSA
+		// This is a NULL parameters value which is required by
+		// https://tools.ietf.org/html/rfc3279#section-2.3.1.
+		publicKeyAlgorithm.Parameters = asn1.RawValue{
+			Tag: 5,
+		}
+	case *ecdsa.PublicKey:
+		publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
+		oid, ok := oidFromNamedCurve(pub.Curve)
+		if !ok {
+			return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported elliptic curve")
+		}
+		publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
+		var paramBytes []byte
+		paramBytes, err = asn1.Marshal(oid)
+		if err != nil {
+			return
+		}
+		publicKeyAlgorithm.Parameters.FullBytes = paramBytes
+	case *PublicKey:
+		publicKeyBytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
+		oid, ok := oidFromNamedCurve(pub.Curve)
+		if !ok {
+			return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported SM2 curve")
+		}
+		publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
+		var paramBytes []byte
+		paramBytes, err = asn1.Marshal(oid)
+		if err != nil {
+			return
+		}
+		publicKeyAlgorithm.Parameters.FullBytes = paramBytes
+	default:
+		return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: only RSA and ECDSA(SM2) public keys supported")
+	}
+
+	return publicKeyBytes, publicKeyAlgorithm, nil
+}
+
+// MarshalPKIXPublicKey serialises a public key to DER-encoded PKIX format.
+func MarshalPKIXPublicKey(pub interface{}) ([]byte, error) {
+	var publicKeyBytes []byte
+	var publicKeyAlgorithm pkix.AlgorithmIdentifier
+	var err error
+
+	if publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(pub); err != nil {
+		return nil, err
+	}
+
+	pkix := pkixPublicKey{
+		Algo: publicKeyAlgorithm,
+		BitString: asn1.BitString{
+			Bytes:     publicKeyBytes,
+			BitLength: 8 * len(publicKeyBytes),
+		},
+	}
+
+	ret, _ := asn1.Marshal(pkix)
+	return ret, nil
+}
+
+// These structures reflect the ASN.1 structure of X.509 certificates.:
+
+type certificate struct {
+	Raw                asn1.RawContent
+	TBSCertificate     tbsCertificate
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	SignatureValue     asn1.BitString
+}
+
+type tbsCertificate struct {
+	Raw                asn1.RawContent
+	Version            int `asn1:"optional,explicit,default:0,tag:0"`
+	SerialNumber       *big.Int
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	Issuer             asn1.RawValue
+	Validity           validity
+	Subject            asn1.RawValue
+	PublicKey          publicKeyInfo
+	UniqueId           asn1.BitString   `asn1:"optional,tag:1"`
+	SubjectUniqueId    asn1.BitString   `asn1:"optional,tag:2"`
+	Extensions         []pkix.Extension `asn1:"optional,explicit,tag:3"`
+}
+
+type dsaAlgorithmParameters struct {
+	P, Q, G *big.Int
+}
+
+type dsaSignature struct {
+	R, S *big.Int
+}
+
+type ecdsaSignature dsaSignature
+
+type validity struct {
+	NotBefore, NotAfter time.Time
+}
+
+type publicKeyInfo struct {
+	Raw       asn1.RawContent
+	Algorithm pkix.AlgorithmIdentifier
+	PublicKey asn1.BitString
+}
+
+// RFC 5280,  4.2.1.1
+type authKeyId struct {
+	Id []byte `asn1:"optional,tag:0"`
+}
+
+type SignatureAlgorithm int
+
+type Hash uint
+
+func init() {
+	RegisterHash(MD4, nil)
+	RegisterHash(MD5, md5.New)
+	RegisterHash(SHA1, sha1.New)
+	RegisterHash(SHA224, sha256.New224)
+	RegisterHash(SHA256, sha256.New)
+	RegisterHash(SHA384, sha512.New384)
+	RegisterHash(SHA512, sha512.New)
+	RegisterHash(MD5SHA1, nil)
+	RegisterHash(RIPEMD160, ripemd160.New)
+	RegisterHash(SHA3_224, sha3.New224)
+	RegisterHash(SHA3_256, sha3.New256)
+	RegisterHash(SHA3_384, sha3.New384)
+	RegisterHash(SHA3_512, sha3.New512)
+	RegisterHash(SHA512_224, sha512.New512_224)
+	RegisterHash(SHA512_256, sha512.New512_256)
+	RegisterHash(SM3, sm3.New)
+}
+
+// HashFunc simply returns the value of h so that Hash implements SignerOpts.
+func (h Hash) HashFunc() crypto.Hash {
+	return crypto.Hash(h)
+}
+
+const (
+	MD4        Hash = 1 + iota // import golang.org/x/crypto/md4
+	MD5                        // import crypto/md5
+	SHA1                       // import crypto/sha1
+	SHA224                     // import crypto/sha256
+	SHA256                     // import crypto/sha256
+	SHA384                     // import crypto/sha512
+	SHA512                     // import crypto/sha512
+	MD5SHA1                    // no implementation; MD5+SHA1 used for TLS RSA
+	RIPEMD160                  // import golang.org/x/crypto/ripemd160
+	SHA3_224                   // import golang.org/x/crypto/sha3
+	SHA3_256                   // import golang.org/x/crypto/sha3
+	SHA3_384                   // import golang.org/x/crypto/sha3
+	SHA3_512                   // import golang.org/x/crypto/sha3
+	SHA512_224                 // import crypto/sha512
+	SHA512_256                 // import crypto/sha512
+	SM3
+	maxHash
+)
+
+var digestSizes = []uint8{
+	MD4:        16,
+	MD5:        16,
+	SHA1:       20,
+	SHA224:     28,
+	SHA256:     32,
+	SHA384:     48,
+	SHA512:     64,
+	SHA512_224: 28,
+	SHA512_256: 32,
+	SHA3_224:   28,
+	SHA3_256:   32,
+	SHA3_384:   48,
+	SHA3_512:   64,
+	MD5SHA1:    36,
+	RIPEMD160:  20,
+	SM3:        32,
+}
+
+// Size returns the length, in bytes, of a digest resulting from the given hash
+// function. It doesn't require that the hash function in question be linked
+// into the program.
+func (h Hash) Size() int {
+	if h > 0 && h < maxHash {
+		return int(digestSizes[h])
+	}
+	panic("crypto: Size of unknown hash function")
+}
+
+var hashes = make([]func() hash.Hash, maxHash)
+
+// New returns a new hash.Hash calculating the given hash function. New panics
+// if the hash function is not linked into the binary.
+func (h Hash) New() hash.Hash {
+	if h > 0 && h < maxHash {
+		f := hashes[h]
+		if f != nil {
+			return f()
+		}
+	}
+	panic("crypto: requested hash function #" + strconv.Itoa(int(h)) + " is unavailable")
+}
+
+// Available reports whether the given hash function is linked into the binary.
+func (h Hash) Available() bool {
+	return h < maxHash && hashes[h] != nil
+}
+
+// RegisterHash registers a function that returns a new instance of the given
+// hash function. This is intended to be called from the init function in
+// packages that implement hash functions.
+func RegisterHash(h Hash, f func() hash.Hash) {
+	if h >= maxHash {
+		panic("crypto: RegisterHash of unknown hash function")
+	}
+	hashes[h] = f
+}
+
+const (
+	UnknownSignatureAlgorithm SignatureAlgorithm = iota
+	MD2WithRSA
+	MD5WithRSA
+	//	SM3WithRSA reserve
+	SHA1WithRSA
+	SHA256WithRSA
+	SHA384WithRSA
+	SHA512WithRSA
+	DSAWithSHA1
+	DSAWithSHA256
+	ECDSAWithSHA1
+	ECDSAWithSHA256
+	ECDSAWithSHA384
+	ECDSAWithSHA512
+	SHA256WithRSAPSS
+	SHA384WithRSAPSS
+	SHA512WithRSAPSS
+	SM2WithSM3
+	SM2WithSHA1
+	SM2WithSHA256
+)
+
+func (algo SignatureAlgorithm) isRSAPSS() bool {
+	switch algo {
+	case SHA256WithRSAPSS, SHA384WithRSAPSS, SHA512WithRSAPSS:
+		return true
+	default:
+		return false
+	}
+}
+
+var algoName = [...]string{
+	MD2WithRSA:  "MD2-RSA",
+	MD5WithRSA:  "MD5-RSA",
+	SHA1WithRSA: "SHA1-RSA",
+	//	SM3WithRSA:       "SM3-RSA", reserve
+	SHA256WithRSA:    "SHA256-RSA",
+	SHA384WithRSA:    "SHA384-RSA",
+	SHA512WithRSA:    "SHA512-RSA",
+	SHA256WithRSAPSS: "SHA256-RSAPSS",
+	SHA384WithRSAPSS: "SHA384-RSAPSS",
+	SHA512WithRSAPSS: "SHA512-RSAPSS",
+	DSAWithSHA1:      "DSA-SHA1",
+	DSAWithSHA256:    "DSA-SHA256",
+	ECDSAWithSHA1:    "ECDSA-SHA1",
+	ECDSAWithSHA256:  "ECDSA-SHA256",
+	ECDSAWithSHA384:  "ECDSA-SHA384",
+	ECDSAWithSHA512:  "ECDSA-SHA512",
+	SM2WithSM3:       "SM2-SM3",
+	SM2WithSHA1:      "SM2-SHA1",
+	SM2WithSHA256:    "SM2-SHA256",
+}
+
+func (algo SignatureAlgorithm) String() string {
+	if 0 < algo && int(algo) < len(algoName) {
+		return algoName[algo]
+	}
+	return strconv.Itoa(int(algo))
+}
+
+type PublicKeyAlgorithm int
+
+const (
+	UnknownPublicKeyAlgorithm PublicKeyAlgorithm = iota
+	RSA
+	DSA
+	ECDSA
+)
+
+// OIDs for signature algorithms
+//
+// pkcs-1 OBJECT IDENTIFIER ::= {
+//    iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 1 }
+//
+//
+// RFC 3279 2.2.1 RSA Signature Algorithms
+//
+// md2WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 2 }
+//
+// md5WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 4 }
+//
+// sha-1WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 5 }
+//
+// dsaWithSha1 OBJECT IDENTIFIER ::= {
+//    iso(1) member-body(2) us(840) x9-57(10040) x9cm(4) 3 }
+//
+// RFC 3279 2.2.3 ECDSA Signature Algorithm
+//
+// ecdsa-with-SHA1 OBJECT IDENTIFIER ::= {
+// 	  iso(1) member-body(2) us(840) ansi-x962(10045)
+//    signatures(4) ecdsa-with-SHA1(1)}
+//
+//
+// RFC 4055 5 PKCS #1 Version 1.5
+//
+// sha256WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 11 }
+//
+// sha384WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 12 }
+//
+// sha512WithRSAEncryption OBJECT IDENTIFIER ::= { pkcs-1 13 }
+//
+//
+// RFC 5758 3.1 DSA Signature Algorithms
+//
+// dsaWithSha256 OBJECT IDENTIFIER ::= {
+//    joint-iso-ccitt(2) country(16) us(840) organization(1) gov(101)
+//    csor(3) algorithms(4) id-dsa-with-sha2(3) 2}
+//
+// RFC 5758 3.2 ECDSA Signature Algorithm
+//
+// ecdsa-with-SHA256 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2 }
+//
+// ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 3 }
+//
+// ecdsa-with-SHA512 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+//    us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4 }
+
+var (
+	oidSignatureMD2WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 2}
+	oidSignatureMD5WithRSA      = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 4}
+	oidSignatureSHA1WithRSA     = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
+	oidSignatureSHA256WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
+	oidSignatureSHA384WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
+	oidSignatureSHA512WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
+	oidSignatureRSAPSS          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 10}
+	oidSignatureDSAWithSHA1     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}
+	oidSignatureDSAWithSHA256   = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 2}
+	oidSignatureECDSAWithSHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
+	oidSignatureECDSAWithSHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
+	oidSignatureECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
+	oidSignatureECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
+	oidSignatureSM2WithSM3      = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 501}
+	oidSignatureSM2WithSHA1     = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 502}
+	oidSignatureSM2WithSHA256   = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 503}
+	//	oidSignatureSM3WithRSA      = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 504}
+
+	oidSM3    = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 401, 1}
+	oidSHA256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 1}
+	oidSHA384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 2}
+	oidSHA512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 3}
+
+	oidMGF1 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 8}
+
+	// oidISOSignatureSHA1WithRSA means the same as oidSignatureSHA1WithRSA
+	// but it's specified by ISO. Microsoft's makecert.exe has been known
+	// to produce certificates with this OID.
+	oidISOSignatureSHA1WithRSA = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 29}
+)
+
+var signatureAlgorithmDetails = []struct {
+	algo       SignatureAlgorithm
+	oid        asn1.ObjectIdentifier
+	pubKeyAlgo PublicKeyAlgorithm
+	hash       Hash
+}{
+	{MD2WithRSA, oidSignatureMD2WithRSA, RSA, Hash(0) /* no value for MD2 */},
+	{MD5WithRSA, oidSignatureMD5WithRSA, RSA, MD5},
+	{SHA1WithRSA, oidSignatureSHA1WithRSA, RSA, SHA1},
+	{SHA1WithRSA, oidISOSignatureSHA1WithRSA, RSA, SHA1},
+	{SHA256WithRSA, oidSignatureSHA256WithRSA, RSA, SHA256},
+	{SHA384WithRSA, oidSignatureSHA384WithRSA, RSA, SHA384},
+	{SHA512WithRSA, oidSignatureSHA512WithRSA, RSA, SHA512},
+	{SHA256WithRSAPSS, oidSignatureRSAPSS, RSA, SHA256},
+	{SHA384WithRSAPSS, oidSignatureRSAPSS, RSA, SHA384},
+	{SHA512WithRSAPSS, oidSignatureRSAPSS, RSA, SHA512},
+	{DSAWithSHA1, oidSignatureDSAWithSHA1, DSA, SHA1},
+	{DSAWithSHA256, oidSignatureDSAWithSHA256, DSA, SHA256},
+	{ECDSAWithSHA1, oidSignatureECDSAWithSHA1, ECDSA, SHA1},
+	{ECDSAWithSHA256, oidSignatureECDSAWithSHA256, ECDSA, SHA256},
+	{ECDSAWithSHA384, oidSignatureECDSAWithSHA384, ECDSA, SHA384},
+	{ECDSAWithSHA512, oidSignatureECDSAWithSHA512, ECDSA, SHA512},
+	{SM2WithSM3, oidSignatureSM2WithSM3, ECDSA, SM3},
+	{SM2WithSHA1, oidSignatureSM2WithSHA1, ECDSA, SHA1},
+	{SM2WithSHA256, oidSignatureSM2WithSHA256, ECDSA, SHA256},
+	//	{SM3WithRSA, oidSignatureSM3WithRSA, RSA, SM3},
+}
+
+// pssParameters reflects the parameters in an AlgorithmIdentifier that
+// specifies RSA PSS. See https://tools.ietf.org/html/rfc3447#appendix-A.2.3
+type pssParameters struct {
+	// The following three fields are not marked as
+	// optional because the default values specify SHA-1,
+	// which is no longer suitable for use in signatures.
+	Hash         pkix.AlgorithmIdentifier `asn1:"explicit,tag:0"`
+	MGF          pkix.AlgorithmIdentifier `asn1:"explicit,tag:1"`
+	SaltLength   int                      `asn1:"explicit,tag:2"`
+	TrailerField int                      `asn1:"optional,explicit,tag:3,default:1"`
+}
+
+// rsaPSSParameters returns an asn1.RawValue suitable for use as the Parameters
+// in an AlgorithmIdentifier that specifies RSA PSS.
+func rsaPSSParameters(hashFunc Hash) asn1.RawValue {
+	var hashOID asn1.ObjectIdentifier
+
+	switch hashFunc {
+	case SHA256:
+		hashOID = oidSHA256
+	case SHA384:
+		hashOID = oidSHA384
+	case SHA512:
+		hashOID = oidSHA512
+	}
+
+	params := pssParameters{
+		Hash: pkix.AlgorithmIdentifier{
+			Algorithm: hashOID,
+			Parameters: asn1.RawValue{
+				Tag: 5, /* ASN.1 NULL */
+			},
+		},
+		MGF: pkix.AlgorithmIdentifier{
+			Algorithm: oidMGF1,
+		},
+		SaltLength:   hashFunc.Size(),
+		TrailerField: 1,
+	}
+
+	mgf1Params := pkix.AlgorithmIdentifier{
+		Algorithm: hashOID,
+		Parameters: asn1.RawValue{
+			Tag: 5, /* ASN.1 NULL */
+		},
+	}
+
+	var err error
+	params.MGF.Parameters.FullBytes, err = asn1.Marshal(mgf1Params)
+	if err != nil {
+		panic(err)
+	}
+
+	serialized, err := asn1.Marshal(params)
+	if err != nil {
+		panic(err)
+	}
+
+	return asn1.RawValue{FullBytes: serialized}
+}
+
+func getSignatureAlgorithmFromAI(ai pkix.AlgorithmIdentifier) SignatureAlgorithm {
+	if !ai.Algorithm.Equal(oidSignatureRSAPSS) {
+		for _, details := range signatureAlgorithmDetails {
+			if ai.Algorithm.Equal(details.oid) {
+				return details.algo
+			}
+		}
+		return UnknownSignatureAlgorithm
+	}
+
+	// RSA PSS is special because it encodes important parameters
+	// in the Parameters.
+
+	var params pssParameters
+	if _, err := asn1.Unmarshal(ai.Parameters.FullBytes, &params); err != nil {
+		return UnknownSignatureAlgorithm
+	}
+
+	var mgf1HashFunc pkix.AlgorithmIdentifier
+	if _, err := asn1.Unmarshal(params.MGF.Parameters.FullBytes, &mgf1HashFunc); err != nil {
+		return UnknownSignatureAlgorithm
+	}
+
+	// PSS is greatly overburdened with options. This code forces
+	// them into three buckets by requiring that the MGF1 hash
+	// function always match the message hash function (as
+	// recommended in
+	// https://tools.ietf.org/html/rfc3447#section-8.1), that the
+	// salt length matches the hash length, and that the trailer
+	// field has the default value.
+	asn1NULL := []byte{0x05, 0x00}
+	if !bytes.Equal(params.Hash.Parameters.FullBytes, asn1NULL) ||
+		!params.MGF.Algorithm.Equal(oidMGF1) ||
+		!mgf1HashFunc.Algorithm.Equal(params.Hash.Algorithm) ||
+		!bytes.Equal(mgf1HashFunc.Parameters.FullBytes, asn1NULL) ||
+		params.TrailerField != 1 {
+		return UnknownSignatureAlgorithm
+	}
+
+	switch {
+	case params.Hash.Algorithm.Equal(oidSHA256) && params.SaltLength == 32:
+		return SHA256WithRSAPSS
+	case params.Hash.Algorithm.Equal(oidSHA384) && params.SaltLength == 48:
+		return SHA384WithRSAPSS
+	case params.Hash.Algorithm.Equal(oidSHA512) && params.SaltLength == 64:
+		return SHA512WithRSAPSS
+	}
+
+	return UnknownSignatureAlgorithm
+}
+
+// RFC 3279, 2.3 Public Key Algorithms
+//
+// pkcs-1 OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
+//    rsadsi(113549) pkcs(1) 1 }
+//
+// rsaEncryption OBJECT IDENTIFIER ::== { pkcs1-1 1 }
+//
+// id-dsa OBJECT IDENTIFIER ::== { iso(1) member-body(2) us(840)
+//    x9-57(10040) x9cm(4) 1 }
+//
+// RFC 5480, 2.1.1 Unrestricted Algorithm Identifier and Parameters
+//
+// id-ecPublicKey OBJECT IDENTIFIER ::= {
+//       iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
+var (
+	oidPublicKeyRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
+	oidPublicKeyDSA   = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
+	oidPublicKeyECDSA = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
+)
+
+func getPublicKeyAlgorithmFromOID(oid asn1.ObjectIdentifier) PublicKeyAlgorithm {
+	switch {
+	case oid.Equal(oidPublicKeyRSA):
+		return RSA
+	case oid.Equal(oidPublicKeyDSA):
+		return DSA
+	case oid.Equal(oidPublicKeyECDSA):
+		return ECDSA
+	}
+	return UnknownPublicKeyAlgorithm
+}
+
+// RFC 5480, 2.1.1.1. Named Curve
+//
+// secp224r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 33 }
+//
+// secp256r1 OBJECT IDENTIFIER ::= {
+//   iso(1) member-body(2) us(840) ansi-X9-62(10045) curves(3)
+//   prime(1) 7 }
+//
+// secp384r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 34 }
+//
+// secp521r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 35 }
+//
+// NB: secp256r1 is equivalent to prime256v1
+var (
+	oidNamedCurveP224    = asn1.ObjectIdentifier{1, 3, 132, 0, 33}
+	oidNamedCurveP256    = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
+	oidNamedCurveP384    = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
+	oidNamedCurveP521    = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
+	oidNamedCurveP256SM2 = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 301} // I get the SM2 ID through parsing the pem file generated by gmssl
+)
+
+func namedCurveFromOID(oid asn1.ObjectIdentifier) elliptic.Curve {
+	switch {
+	case oid.Equal(oidNamedCurveP224):
+		return elliptic.P224()
+	case oid.Equal(oidNamedCurveP256):
+		return elliptic.P256()
+	case oid.Equal(oidNamedCurveP384):
+		return elliptic.P384()
+	case oid.Equal(oidNamedCurveP521):
+		return elliptic.P521()
+	case oid.Equal(oidNamedCurveP256SM2):
+		return P256Sm2()
+	}
+	return nil
+}
+
+func oidFromNamedCurve(curve elliptic.Curve) (asn1.ObjectIdentifier, bool) {
+	switch curve {
+	case elliptic.P224():
+		return oidNamedCurveP224, true
+	case elliptic.P256():
+		return oidNamedCurveP256, true
+	case elliptic.P384():
+		return oidNamedCurveP384, true
+	case elliptic.P521():
+		return oidNamedCurveP521, true
+	case P256Sm2():
+		return oidNamedCurveP256SM2, true
+	}
+	return nil, false
+}
+
+// KeyUsage represents the set of actions that are valid for a given key. It's
+// a bitmap of the KeyUsage* constants.
+type KeyUsage int
+
+const (
+	KeyUsageDigitalSignature KeyUsage = 1 << iota
+	KeyUsageContentCommitment
+	KeyUsageKeyEncipherment
+	KeyUsageDataEncipherment
+	KeyUsageKeyAgreement
+	KeyUsageCertSign
+	KeyUsageCRLSign
+	KeyUsageEncipherOnly
+	KeyUsageDecipherOnly
+)
+
+// RFC 5280, 4.2.1.12  Extended Key Usage
+//
+// anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 }
+//
+// id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
+//
+// id-kp-serverAuth             OBJECT IDENTIFIER ::= { id-kp 1 }
+// id-kp-clientAuth             OBJECT IDENTIFIER ::= { id-kp 2 }
+// id-kp-codeSigning            OBJECT IDENTIFIER ::= { id-kp 3 }
+// id-kp-emailProtection        OBJECT IDENTIFIER ::= { id-kp 4 }
+// id-kp-timeStamping           OBJECT IDENTIFIER ::= { id-kp 8 }
+// id-kp-OCSPSigning            OBJECT IDENTIFIER ::= { id-kp 9 }
+var (
+	oidExtKeyUsageAny                        = asn1.ObjectIdentifier{2, 5, 29, 37, 0}
+	oidExtKeyUsageServerAuth                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 1}
+	oidExtKeyUsageClientAuth                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 2}
+	oidExtKeyUsageCodeSigning                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 3}
+	oidExtKeyUsageEmailProtection            = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 4}
+	oidExtKeyUsageIPSECEndSystem             = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 5}
+	oidExtKeyUsageIPSECTunnel                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 6}
+	oidExtKeyUsageIPSECUser                  = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 7}
+	oidExtKeyUsageTimeStamping               = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 8}
+	oidExtKeyUsageOCSPSigning                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 9}
+	oidExtKeyUsageMicrosoftServerGatedCrypto = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 10, 3, 3}
+	oidExtKeyUsageNetscapeServerGatedCrypto  = asn1.ObjectIdentifier{2, 16, 840, 1, 113730, 4, 1}
+)
+
+// ExtKeyUsage represents an extended set of actions that are valid for a given key.
+// Each of the ExtKeyUsage* constants define a unique action.
+type ExtKeyUsage int
+
+const (
+	ExtKeyUsageAny ExtKeyUsage = iota
+	ExtKeyUsageServerAuth
+	ExtKeyUsageClientAuth
+	ExtKeyUsageCodeSigning
+	ExtKeyUsageEmailProtection
+	ExtKeyUsageIPSECEndSystem
+	ExtKeyUsageIPSECTunnel
+	ExtKeyUsageIPSECUser
+	ExtKeyUsageTimeStamping
+	ExtKeyUsageOCSPSigning
+	ExtKeyUsageMicrosoftServerGatedCrypto
+	ExtKeyUsageNetscapeServerGatedCrypto
+)
+
+// extKeyUsageOIDs contains the mapping between an ExtKeyUsage and its OID.
+var extKeyUsageOIDs = []struct {
+	extKeyUsage ExtKeyUsage
+	oid         asn1.ObjectIdentifier
+}{
+	{ExtKeyUsageAny, oidExtKeyUsageAny},
+	{ExtKeyUsageServerAuth, oidExtKeyUsageServerAuth},
+	{ExtKeyUsageClientAuth, oidExtKeyUsageClientAuth},
+	{ExtKeyUsageCodeSigning, oidExtKeyUsageCodeSigning},
+	{ExtKeyUsageEmailProtection, oidExtKeyUsageEmailProtection},
+	{ExtKeyUsageIPSECEndSystem, oidExtKeyUsageIPSECEndSystem},
+	{ExtKeyUsageIPSECTunnel, oidExtKeyUsageIPSECTunnel},
+	{ExtKeyUsageIPSECUser, oidExtKeyUsageIPSECUser},
+	{ExtKeyUsageTimeStamping, oidExtKeyUsageTimeStamping},
+	{ExtKeyUsageOCSPSigning, oidExtKeyUsageOCSPSigning},
+	{ExtKeyUsageMicrosoftServerGatedCrypto, oidExtKeyUsageMicrosoftServerGatedCrypto},
+	{ExtKeyUsageNetscapeServerGatedCrypto, oidExtKeyUsageNetscapeServerGatedCrypto},
+}
+
+func extKeyUsageFromOID(oid asn1.ObjectIdentifier) (eku ExtKeyUsage, ok bool) {
+	for _, pair := range extKeyUsageOIDs {
+		if oid.Equal(pair.oid) {
+			return pair.extKeyUsage, true
+		}
+	}
+	return
+}
+
+func oidFromExtKeyUsage(eku ExtKeyUsage) (oid asn1.ObjectIdentifier, ok bool) {
+	for _, pair := range extKeyUsageOIDs {
+		if eku == pair.extKeyUsage {
+			return pair.oid, true
+		}
+	}
+	return
+}
+
+// A Certificate represents an X.509 certificate.
+type Certificate struct {
+	Raw                     []byte // Complete ASN.1 DER content (certificate, signature algorithm and signature).
+	RawTBSCertificate       []byte // Certificate part of raw ASN.1 DER content.
+	RawSubjectPublicKeyInfo []byte // DER encoded SubjectPublicKeyInfo.
+	RawSubject              []byte // DER encoded Subject
+	RawIssuer               []byte // DER encoded Issuer
+
+	Signature          []byte
+	SignatureAlgorithm SignatureAlgorithm
+
+	PublicKeyAlgorithm PublicKeyAlgorithm
+	PublicKey          interface{}
+
+	Version             int
+	SerialNumber        *big.Int
+	Issuer              pkix.Name
+	Subject             pkix.Name
+	NotBefore, NotAfter time.Time // Validity bounds.
+	KeyUsage            KeyUsage
+
+	// Extensions contains raw X.509 extensions. When parsing certificates,
+	// this can be used to extract non-critical extensions that are not
+	// parsed by this package. When marshaling certificates, the Extensions
+	// field is ignored, see ExtraExtensions.
+	Extensions []pkix.Extension
+
+	// ExtraExtensions contains extensions to be copied, raw, into any
+	// marshaled certificates. Values override any extensions that would
+	// otherwise be produced based on the other fields. The ExtraExtensions
+	// field is not populated when parsing certificates, see Extensions.
+	ExtraExtensions []pkix.Extension
+
+	// UnhandledCriticalExtensions contains a list of extension IDs that
+	// were not (fully) processed when parsing. Verify will fail if this
+	// slice is non-empty, unless verification is delegated to an OS
+	// library which understands all the critical extensions.
+	//
+	// Users can access these extensions using Extensions and can remove
+	// elements from this slice if they believe that they have been
+	// handled.
+	UnhandledCriticalExtensions []asn1.ObjectIdentifier
+
+	ExtKeyUsage        []ExtKeyUsage           // Sequence of extended key usages.
+	UnknownExtKeyUsage []asn1.ObjectIdentifier // Encountered extended key usages unknown to this package.
+
+	BasicConstraintsValid bool // if true then the next two fields are valid.
+	IsCA                  bool
+	MaxPathLen            int
+	// MaxPathLenZero indicates that BasicConstraintsValid==true and
+	// MaxPathLen==0 should be interpreted as an actual maximum path length
+	// of zero. Otherwise, that combination is interpreted as MaxPathLen
+	// not being set.
+	MaxPathLenZero bool
+
+	SubjectKeyId   []byte
+	AuthorityKeyId []byte
+
+	// RFC 5280, 4.2.2.1 (Authority Information Access)
+	OCSPServer            []string
+	IssuingCertificateURL []string
+
+	// Subject Alternate Name values
+	DNSNames       []string
+	EmailAddresses []string
+	IPAddresses    []net.IP
+
+	// Name constraints
+	PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
+	PermittedDNSDomains         []string
+
+	// CRL Distribution Points
+	CRLDistributionPoints []string
+
+	PolicyIdentifiers []asn1.ObjectIdentifier
+}
+
+// ErrUnsupportedAlgorithm results from attempting to perform an operation that
+// involves algorithms that are not currently implemented.
+var ErrUnsupportedAlgorithm = errors.New("x509: cannot verify signature: algorithm unimplemented")
+
+// An InsecureAlgorithmError
+type InsecureAlgorithmError SignatureAlgorithm
+
+func (e InsecureAlgorithmError) Error() string {
+	return fmt.Sprintf("x509: cannot verify signature: insecure algorithm %v", SignatureAlgorithm(e))
+}
+
+// ConstraintViolationError results when a requested usage is not permitted by
+// a certificate. For example: checking a signature when the public key isn't a
+// certificate signing key.
+type ConstraintViolationError struct{}
+
+func (ConstraintViolationError) Error() string {
+	return "x509: invalid signature: parent certificate cannot sign this kind of certificate"
+}
+
+func (c *Certificate) Equal(other *Certificate) bool {
+	return bytes.Equal(c.Raw, other.Raw)
+}
+
+// Entrust have a broken root certificate (CN=Entrust.net Certification
+// Authority (2048)) which isn't marked as a CA certificate and is thus invalid
+// according to PKIX.
+// We recognise this certificate by its SubjectPublicKeyInfo and exempt it
+// from the Basic Constraints requirement.
+// See http://www.entrust.net/knowledge-base/technote.cfm?tn=7869
+//
+// TODO(agl): remove this hack once their reissued root is sufficiently
+// widespread.
+var entrustBrokenSPKI = []byte{
+	0x30, 0x82, 0x01, 0x22, 0x30, 0x0d, 0x06, 0x09,
+	0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
+	0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x0f, 0x00,
+	0x30, 0x82, 0x01, 0x0a, 0x02, 0x82, 0x01, 0x01,
+	0x00, 0x97, 0xa3, 0x2d, 0x3c, 0x9e, 0xde, 0x05,
+	0xda, 0x13, 0xc2, 0x11, 0x8d, 0x9d, 0x8e, 0xe3,
+	0x7f, 0xc7, 0x4b, 0x7e, 0x5a, 0x9f, 0xb3, 0xff,
+	0x62, 0xab, 0x73, 0xc8, 0x28, 0x6b, 0xba, 0x10,
+	0x64, 0x82, 0x87, 0x13, 0xcd, 0x57, 0x18, 0xff,
+	0x28, 0xce, 0xc0, 0xe6, 0x0e, 0x06, 0x91, 0x50,
+	0x29, 0x83, 0xd1, 0xf2, 0xc3, 0x2a, 0xdb, 0xd8,
+	0xdb, 0x4e, 0x04, 0xcc, 0x00, 0xeb, 0x8b, 0xb6,
+	0x96, 0xdc, 0xbc, 0xaa, 0xfa, 0x52, 0x77, 0x04,
+	0xc1, 0xdb, 0x19, 0xe4, 0xae, 0x9c, 0xfd, 0x3c,
+	0x8b, 0x03, 0xef, 0x4d, 0xbc, 0x1a, 0x03, 0x65,
+	0xf9, 0xc1, 0xb1, 0x3f, 0x72, 0x86, 0xf2, 0x38,
+	0xaa, 0x19, 0xae, 0x10, 0x88, 0x78, 0x28, 0xda,
+	0x75, 0xc3, 0x3d, 0x02, 0x82, 0x02, 0x9c, 0xb9,
+	0xc1, 0x65, 0x77, 0x76, 0x24, 0x4c, 0x98, 0xf7,
+	0x6d, 0x31, 0x38, 0xfb, 0xdb, 0xfe, 0xdb, 0x37,
+	0x02, 0x76, 0xa1, 0x18, 0x97, 0xa6, 0xcc, 0xde,
+	0x20, 0x09, 0x49, 0x36, 0x24, 0x69, 0x42, 0xf6,
+	0xe4, 0x37, 0x62, 0xf1, 0x59, 0x6d, 0xa9, 0x3c,
+	0xed, 0x34, 0x9c, 0xa3, 0x8e, 0xdb, 0xdc, 0x3a,
+	0xd7, 0xf7, 0x0a, 0x6f, 0xef, 0x2e, 0xd8, 0xd5,
+	0x93, 0x5a, 0x7a, 0xed, 0x08, 0x49, 0x68, 0xe2,
+	0x41, 0xe3, 0x5a, 0x90, 0xc1, 0x86, 0x55, 0xfc,
+	0x51, 0x43, 0x9d, 0xe0, 0xb2, 0xc4, 0x67, 0xb4,
+	0xcb, 0x32, 0x31, 0x25, 0xf0, 0x54, 0x9f, 0x4b,
+	0xd1, 0x6f, 0xdb, 0xd4, 0xdd, 0xfc, 0xaf, 0x5e,
+	0x6c, 0x78, 0x90, 0x95, 0xde, 0xca, 0x3a, 0x48,
+	0xb9, 0x79, 0x3c, 0x9b, 0x19, 0xd6, 0x75, 0x05,
+	0xa0, 0xf9, 0x88, 0xd7, 0xc1, 0xe8, 0xa5, 0x09,
+	0xe4, 0x1a, 0x15, 0xdc, 0x87, 0x23, 0xaa, 0xb2,
+	0x75, 0x8c, 0x63, 0x25, 0x87, 0xd8, 0xf8, 0x3d,
+	0xa6, 0xc2, 0xcc, 0x66, 0xff, 0xa5, 0x66, 0x68,
+	0x55, 0x02, 0x03, 0x01, 0x00, 0x01,
+}
+
+// CheckSignatureFrom verifies that the signature on c is a valid signature
+// from parent.
+func (c *Certificate) CheckSignatureFrom(parent *Certificate) error {
+	// RFC 5280, 4.2.1.9:
+	// "If the basic constraints extension is not present in a version 3
+	// certificate, or the extension is present but the cA boolean is not
+	// asserted, then the certified public key MUST NOT be used to verify
+	// certificate signatures."
+	// (except for Entrust, see comment above entrustBrokenSPKI)
+	if (parent.Version == 3 && !parent.BasicConstraintsValid ||
+		parent.BasicConstraintsValid && !parent.IsCA) &&
+		!bytes.Equal(c.RawSubjectPublicKeyInfo, entrustBrokenSPKI) {
+		return ConstraintViolationError{}
+	}
+
+	if parent.KeyUsage != 0 && parent.KeyUsage&KeyUsageCertSign == 0 {
+		return ConstraintViolationError{}
+	}
+
+	if parent.PublicKeyAlgorithm == UnknownPublicKeyAlgorithm {
+		return ErrUnsupportedAlgorithm
+	}
+
+	// TODO(agl): don't ignore the path length constraint.
+
+	return parent.CheckSignature(c.SignatureAlgorithm, c.RawTBSCertificate, c.Signature)
+}
+
+// CheckSignature verifies that signature is a valid signature over signed from
+// c's public key.
+func (c *Certificate) CheckSignature(algo SignatureAlgorithm, signed, signature []byte) error {
+	return checkSignature(algo, signed, signature, c.PublicKey)
+}
+
+// CheckSignature verifies that signature is a valid signature over signed from
+// a crypto.PublicKey.
+func checkSignature(algo SignatureAlgorithm, signed, signature []byte, publicKey crypto.PublicKey) (err error) {
+	var hashType Hash
+
+	switch algo {
+	case SHA1WithRSA, DSAWithSHA1, ECDSAWithSHA1, SM2WithSHA1:
+		hashType = SHA1
+	case SHA256WithRSA, SHA256WithRSAPSS, DSAWithSHA256, ECDSAWithSHA256, SM2WithSHA256:
+		hashType = SHA256
+	case SHA384WithRSA, SHA384WithRSAPSS, ECDSAWithSHA384:
+		hashType = SHA384
+	case SHA512WithRSA, SHA512WithRSAPSS, ECDSAWithSHA512:
+		hashType = SHA512
+	case MD2WithRSA, MD5WithRSA:
+		return InsecureAlgorithmError(algo)
+	case SM2WithSM3: // SM3WithRSA reserve
+		hashType = SM3
+	default:
+		return ErrUnsupportedAlgorithm
+	}
+
+	if !hashType.Available() {
+		return ErrUnsupportedAlgorithm
+	}
+	h := hashType.New()
+
+	h.Write(signed)
+	digest := h.Sum(nil)
+
+	switch pub := publicKey.(type) {
+	case *rsa.PublicKey:
+		if algo.isRSAPSS() {
+			return rsa.VerifyPSS(pub, crypto.Hash(hashType), digest, signature, &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash})
+		} else {
+			return rsa.VerifyPKCS1v15(pub, crypto.Hash(hashType), digest, signature)
+		}
+	case *dsa.PublicKey:
+		dsaSig := new(dsaSignature)
+		if rest, err := asn1.Unmarshal(signature, dsaSig); err != nil {
+			return err
+		} else if len(rest) != 0 {
+			return errors.New("x509: trailing data after DSA signature")
+		}
+		if dsaSig.R.Sign() <= 0 || dsaSig.S.Sign() <= 0 {
+			return errors.New("x509: DSA signature contained zero or negative values")
+		}
+		if !dsa.Verify(pub, digest, dsaSig.R, dsaSig.S) {
+			return errors.New("x509: DSA verification failure")
+		}
+		return
+	case *ecdsa.PublicKey:
+		ecdsaSig := new(ecdsaSignature)
+		if rest, err := asn1.Unmarshal(signature, ecdsaSig); err != nil {
+			return err
+		} else if len(rest) != 0 {
+			return errors.New("x509: trailing data after ECDSA signature")
+		}
+		if ecdsaSig.R.Sign() <= 0 || ecdsaSig.S.Sign() <= 0 {
+			return errors.New("x509: ECDSA signature contained zero or negative values")
+		}
+		switch pub.Curve {
+		case P256Sm2():
+			if !Verify(&PublicKey{
+				Curve: pub.Curve,
+				X:     pub.X,
+				Y:     pub.Y,
+			}, digest, ecdsaSig.R, ecdsaSig.S) {
+				return errors.New("x509: SM2 verification failure")
+			}
+		default:
+			if !ecdsa.Verify(pub, digest, ecdsaSig.R, ecdsaSig.S) {
+				return errors.New("x509: ECDSA verification failure")
+			}
+		}
+		return
+	}
+	return ErrUnsupportedAlgorithm
+}
+
+// CheckCRLSignature checks that the signature in crl is from c.
+func (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) error {
+	algo := getSignatureAlgorithmFromAI(crl.SignatureAlgorithm)
+	return c.CheckSignature(algo, crl.TBSCertList.Raw, crl.SignatureValue.RightAlign())
+}
+
+type UnhandledCriticalExtension struct{}
+
+func (h UnhandledCriticalExtension) Error() string {
+	return "x509: unhandled critical extension"
+}
+
+type basicConstraints struct {
+	IsCA       bool `asn1:"optional"`
+	MaxPathLen int  `asn1:"optional,default:-1"`
+}
+
+// RFC 5280 4.2.1.4
+type policyInformation struct {
+	Policy asn1.ObjectIdentifier
+	// policyQualifiers omitted
+}
+
+// RFC 5280, 4.2.1.10
+type nameConstraints struct {
+	Permitted []generalSubtree `asn1:"optional,tag:0"`
+	Excluded  []generalSubtree `asn1:"optional,tag:1"`
+}
+
+type generalSubtree struct {
+	Name string `asn1:"tag:2,optional,ia5"`
+}
+
+// RFC 5280, 4.2.2.1
+type authorityInfoAccess struct {
+	Method   asn1.ObjectIdentifier
+	Location asn1.RawValue
+}
+
+// RFC 5280, 4.2.1.14
+type distributionPoint struct {
+	DistributionPoint distributionPointName `asn1:"optional,tag:0"`
+	Reason            asn1.BitString        `asn1:"optional,tag:1"`
+	CRLIssuer         asn1.RawValue         `asn1:"optional,tag:2"`
+}
+
+type distributionPointName struct {
+	FullName     asn1.RawValue    `asn1:"optional,tag:0"`
+	RelativeName pkix.RDNSequence `asn1:"optional,tag:1"`
+}
+
+// asn1Null is the ASN.1 encoding of a NULL value.
+var asn1Null = []byte{5, 0}
+
+func parsePublicKey(algo PublicKeyAlgorithm, keyData *publicKeyInfo) (interface{}, error) {
+	asn1Data := keyData.PublicKey.RightAlign()
+	switch algo {
+	case RSA:
+		// RSA public keys must have a NULL in the parameters
+		// (https://tools.ietf.org/html/rfc3279#section-2.3.1).
+		if !bytes.Equal(keyData.Algorithm.Parameters.FullBytes, asn1Null) {
+			return nil, errors.New("x509: RSA key missing NULL parameters")
+		}
+
+		p := new(rsaPublicKey)
+		rest, err := asn1.Unmarshal(asn1Data, p)
+		if err != nil {
+			return nil, err
+		}
+		if len(rest) != 0 {
+			return nil, errors.New("x509: trailing data after RSA public key")
+		}
+
+		if p.N.Sign() <= 0 {
+			return nil, errors.New("x509: RSA modulus is not a positive number")
+		}
+		if p.E <= 0 {
+			return nil, errors.New("x509: RSA public exponent is not a positive number")
+		}
+
+		pub := &rsa.PublicKey{
+			E: p.E,
+			N: p.N,
+		}
+		return pub, nil
+	case DSA:
+		var p *big.Int
+		rest, err := asn1.Unmarshal(asn1Data, &p)
+		if err != nil {
+			return nil, err
+		}
+		if len(rest) != 0 {
+			return nil, errors.New("x509: trailing data after DSA public key")
+		}
+		paramsData := keyData.Algorithm.Parameters.FullBytes
+		params := new(dsaAlgorithmParameters)
+		rest, err = asn1.Unmarshal(paramsData, params)
+		if err != nil {
+			return nil, err
+		}
+		if len(rest) != 0 {
+			return nil, errors.New("x509: trailing data after DSA parameters")
+		}
+		if p.Sign() <= 0 || params.P.Sign() <= 0 || params.Q.Sign() <= 0 || params.G.Sign() <= 0 {
+			return nil, errors.New("x509: zero or negative DSA parameter")
+		}
+		pub := &dsa.PublicKey{
+			Parameters: dsa.Parameters{
+				P: params.P,
+				Q: params.Q,
+				G: params.G,
+			},
+			Y: p,
+		}
+		return pub, nil
+	case ECDSA:
+		paramsData := keyData.Algorithm.Parameters.FullBytes
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		rest, err := asn1.Unmarshal(paramsData, namedCurveOID)
+		if err != nil {
+			return nil, err
+		}
+		if len(rest) != 0 {
+			return nil, errors.New("x509: trailing data after ECDSA parameters")
+		}
+		namedCurve := namedCurveFromOID(*namedCurveOID)
+		if namedCurve == nil {
+			return nil, errors.New("x509: unsupported elliptic curve")
+		}
+		x, y := elliptic.Unmarshal(namedCurve, asn1Data)
+		if x == nil {
+			return nil, errors.New("x509: failed to unmarshal elliptic curve point")
+		}
+		pub := &ecdsa.PublicKey{
+			Curve: namedCurve,
+			X:     x,
+			Y:     y,
+		}
+		return pub, nil
+	default:
+		return nil, nil
+	}
+}
+
+func parseSANExtension(value []byte) (dnsNames, emailAddresses []string, ipAddresses []net.IP, err error) {
+	// RFC 5280, 4.2.1.6
+
+	// SubjectAltName ::= GeneralNames
+	//
+	// GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
+	//
+	// GeneralName ::= CHOICE {
+	//      otherName                       [0]     OtherName,
+	//      rfc822Name                      [1]     IA5String,
+	//      dNSName                         [2]     IA5String,
+	//      x400Address                     [3]     ORAddress,
+	//      directoryName                   [4]     Name,
+	//      ediPartyName                    [5]     EDIPartyName,
+	//      uniformResourceIdentifier       [6]     IA5String,
+	//      iPAddress                       [7]     OCTET STRING,
+	//      registeredID                    [8]     OBJECT IDENTIFIER }
+	var seq asn1.RawValue
+	var rest []byte
+	if rest, err = asn1.Unmarshal(value, &seq); err != nil {
+		return
+	} else if len(rest) != 0 {
+		err = errors.New("x509: trailing data after X.509 extension")
+		return
+	}
+	if !seq.IsCompound || seq.Tag != 16 || seq.Class != 0 {
+		err = asn1.StructuralError{Msg: "bad SAN sequence"}
+		return
+	}
+
+	rest = seq.Bytes
+	for len(rest) > 0 {
+		var v asn1.RawValue
+		rest, err = asn1.Unmarshal(rest, &v)
+		if err != nil {
+			return
+		}
+		switch v.Tag {
+		case 1:
+			emailAddresses = append(emailAddresses, string(v.Bytes))
+		case 2:
+			dnsNames = append(dnsNames, string(v.Bytes))
+		case 7:
+			switch len(v.Bytes) {
+			case net.IPv4len, net.IPv6len:
+				ipAddresses = append(ipAddresses, v.Bytes)
+			default:
+				err = errors.New("x509: certificate contained IP address of length " + strconv.Itoa(len(v.Bytes)))
+				return
+			}
+		}
+	}
+
+	return
+}
+
+func parseCertificate(in *certificate) (*Certificate, error) {
+	out := new(Certificate)
+	out.Raw = in.Raw
+	out.RawTBSCertificate = in.TBSCertificate.Raw
+	out.RawSubjectPublicKeyInfo = in.TBSCertificate.PublicKey.Raw
+	out.RawSubject = in.TBSCertificate.Subject.FullBytes
+	out.RawIssuer = in.TBSCertificate.Issuer.FullBytes
+
+	out.Signature = in.SignatureValue.RightAlign()
+	out.SignatureAlgorithm =
+		getSignatureAlgorithmFromAI(in.TBSCertificate.SignatureAlgorithm)
+
+	out.PublicKeyAlgorithm =
+		getPublicKeyAlgorithmFromOID(in.TBSCertificate.PublicKey.Algorithm.Algorithm)
+	var err error
+	out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCertificate.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+
+	out.Version = in.TBSCertificate.Version + 1
+	out.SerialNumber = in.TBSCertificate.SerialNumber
+
+	var issuer, subject pkix.RDNSequence
+	if rest, err := asn1.Unmarshal(in.TBSCertificate.Subject.FullBytes, &subject); err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after X.509 subject")
+	}
+	if rest, err := asn1.Unmarshal(in.TBSCertificate.Issuer.FullBytes, &issuer); err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after X.509 subject")
+	}
+
+	out.Issuer.FillFromRDNSequence(&issuer)
+	out.Subject.FillFromRDNSequence(&subject)
+
+	out.NotBefore = in.TBSCertificate.Validity.NotBefore
+	out.NotAfter = in.TBSCertificate.Validity.NotAfter
+
+	for _, e := range in.TBSCertificate.Extensions {
+		out.Extensions = append(out.Extensions, e)
+		unhandled := false
+
+		if len(e.Id) == 4 && e.Id[0] == 2 && e.Id[1] == 5 && e.Id[2] == 29 {
+			switch e.Id[3] {
+			case 15:
+				// RFC 5280, 4.2.1.3
+				var usageBits asn1.BitString
+				if rest, err := asn1.Unmarshal(e.Value, &usageBits); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 KeyUsage")
+				}
+
+				var usage int
+				for i := 0; i < 9; i++ {
+					if usageBits.At(i) != 0 {
+						usage |= 1 << uint(i)
+					}
+				}
+				out.KeyUsage = KeyUsage(usage)
+
+			case 19:
+				// RFC 5280, 4.2.1.9
+				var constraints basicConstraints
+				if rest, err := asn1.Unmarshal(e.Value, &constraints); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 BasicConstraints")
+				}
+
+				out.BasicConstraintsValid = true
+				out.IsCA = constraints.IsCA
+				out.MaxPathLen = constraints.MaxPathLen
+				out.MaxPathLenZero = out.MaxPathLen == 0
+
+			case 17:
+				out.DNSNames, out.EmailAddresses, out.IPAddresses, err = parseSANExtension(e.Value)
+				if err != nil {
+					return nil, err
+				}
+
+				if len(out.DNSNames) == 0 && len(out.EmailAddresses) == 0 && len(out.IPAddresses) == 0 {
+					// If we didn't parse anything then we do the critical check, below.
+					unhandled = true
+				}
+
+			case 30:
+				// RFC 5280, 4.2.1.10
+
+				// NameConstraints ::= SEQUENCE {
+				//      permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
+				//      excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }
+				//
+				// GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
+				//
+				// GeneralSubtree ::= SEQUENCE {
+				//      base                    GeneralName,
+				//      minimum         [0]     BaseDistance DEFAULT 0,
+				//      maximum         [1]     BaseDistance OPTIONAL }
+				//
+				// BaseDistance ::= INTEGER (0..MAX)
+
+				var constraints nameConstraints
+				if rest, err := asn1.Unmarshal(e.Value, &constraints); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 NameConstraints")
+				}
+
+				if len(constraints.Excluded) > 0 && e.Critical {
+					return out, UnhandledCriticalExtension{}
+				}
+
+				for _, subtree := range constraints.Permitted {
+					if len(subtree.Name) == 0 {
+						if e.Critical {
+							return out, UnhandledCriticalExtension{}
+						}
+						continue
+					}
+					out.PermittedDNSDomains = append(out.PermittedDNSDomains, subtree.Name)
+				}
+
+			case 31:
+				// RFC 5280, 4.2.1.13
+
+				// CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
+				//
+				// DistributionPoint ::= SEQUENCE {
+				//     distributionPoint       [0]     DistributionPointName OPTIONAL,
+				//     reasons                 [1]     ReasonFlags OPTIONAL,
+				//     cRLIssuer               [2]     GeneralNames OPTIONAL }
+				//
+				// DistributionPointName ::= CHOICE {
+				//     fullName                [0]     GeneralNames,
+				//     nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }
+
+				var cdp []distributionPoint
+				if rest, err := asn1.Unmarshal(e.Value, &cdp); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 CRL distribution point")
+				}
+
+				for _, dp := range cdp {
+					// Per RFC 5280, 4.2.1.13, one of distributionPoint or cRLIssuer may be empty.
+					if len(dp.DistributionPoint.FullName.Bytes) == 0 {
+						continue
+					}
+
+					var n asn1.RawValue
+					if _, err := asn1.Unmarshal(dp.DistributionPoint.FullName.Bytes, &n); err != nil {
+						return nil, err
+					}
+					// Trailing data after the fullName is
+					// allowed because other elements of
+					// the SEQUENCE can appear.
+
+					if n.Tag == 6 {
+						out.CRLDistributionPoints = append(out.CRLDistributionPoints, string(n.Bytes))
+					}
+				}
+
+			case 35:
+				// RFC 5280, 4.2.1.1
+				var a authKeyId
+				if rest, err := asn1.Unmarshal(e.Value, &a); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 authority key-id")
+				}
+				out.AuthorityKeyId = a.Id
+
+			case 37:
+				// RFC 5280, 4.2.1.12.  Extended Key Usage
+
+				// id-ce-extKeyUsage OBJECT IDENTIFIER ::= { id-ce 37 }
+				//
+				// ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
+				//
+				// KeyPurposeId ::= OBJECT IDENTIFIER
+
+				var keyUsage []asn1.ObjectIdentifier
+				if rest, err := asn1.Unmarshal(e.Value, &keyUsage); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 ExtendedKeyUsage")
+				}
+
+				for _, u := range keyUsage {
+					if extKeyUsage, ok := extKeyUsageFromOID(u); ok {
+						out.ExtKeyUsage = append(out.ExtKeyUsage, extKeyUsage)
+					} else {
+						out.UnknownExtKeyUsage = append(out.UnknownExtKeyUsage, u)
+					}
+				}
+
+			case 14:
+				// RFC 5280, 4.2.1.2
+				var keyid []byte
+				if rest, err := asn1.Unmarshal(e.Value, &keyid); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 key-id")
+				}
+				out.SubjectKeyId = keyid
+
+			case 32:
+				// RFC 5280 4.2.1.4: Certificate Policies
+				var policies []policyInformation
+				if rest, err := asn1.Unmarshal(e.Value, &policies); err != nil {
+					return nil, err
+				} else if len(rest) != 0 {
+					return nil, errors.New("x509: trailing data after X.509 certificate policies")
+				}
+				out.PolicyIdentifiers = make([]asn1.ObjectIdentifier, len(policies))
+				for i, policy := range policies {
+					out.PolicyIdentifiers[i] = policy.Policy
+				}
+
+			default:
+				// Unknown extensions are recorded if critical.
+				unhandled = true
+			}
+		} else if e.Id.Equal(oidExtensionAuthorityInfoAccess) {
+			// RFC 5280 4.2.2.1: Authority Information Access
+			var aia []authorityInfoAccess
+			if rest, err := asn1.Unmarshal(e.Value, &aia); err != nil {
+				return nil, err
+			} else if len(rest) != 0 {
+				return nil, errors.New("x509: trailing data after X.509 authority information")
+			}
+
+			for _, v := range aia {
+				// GeneralName: uniformResourceIdentifier [6] IA5String
+				if v.Location.Tag != 6 {
+					continue
+				}
+				if v.Method.Equal(oidAuthorityInfoAccessOcsp) {
+					out.OCSPServer = append(out.OCSPServer, string(v.Location.Bytes))
+				} else if v.Method.Equal(oidAuthorityInfoAccessIssuers) {
+					out.IssuingCertificateURL = append(out.IssuingCertificateURL, string(v.Location.Bytes))
+				}
+			}
+		} else {
+			// Unknown extensions are recorded if critical.
+			unhandled = true
+		}
+
+		if e.Critical && unhandled {
+			out.UnhandledCriticalExtensions = append(out.UnhandledCriticalExtensions, e.Id)
+		}
+	}
+
+	return out, nil
+}
+
+// ParseCertificate parses a single certificate from the given ASN.1 DER data.
+func ParseCertificate(asn1Data []byte) (*Certificate, error) {
+	var cert certificate
+	rest, err := asn1.Unmarshal(asn1Data, &cert)
+	if err != nil {
+		return nil, err
+	}
+	if len(rest) > 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+
+	return parseCertificate(&cert)
+}
+
+// ParseCertificates parses one or more certificates from the given ASN.1 DER
+// data. The certificates must be concatenated with no intermediate padding.
+func ParseCertificates(asn1Data []byte) ([]*Certificate, error) {
+	var v []*certificate
+
+	for len(asn1Data) > 0 {
+		cert := new(certificate)
+		var err error
+		asn1Data, err = asn1.Unmarshal(asn1Data, cert)
+		if err != nil {
+			return nil, err
+		}
+		v = append(v, cert)
+	}
+
+	ret := make([]*Certificate, len(v))
+	for i, ci := range v {
+		cert, err := parseCertificate(ci)
+		if err != nil {
+			return nil, err
+		}
+		ret[i] = cert
+	}
+
+	return ret, nil
+}
+
+func reverseBitsInAByte(in byte) byte {
+	b1 := in>>4 | in<<4
+	b2 := b1>>2&0x33 | b1<<2&0xcc
+	b3 := b2>>1&0x55 | b2<<1&0xaa
+	return b3
+}
+
+// asn1BitLength returns the bit-length of bitString by considering the
+// most-significant bit in a byte to be the "first" bit. This convention
+// matches ASN.1, but differs from almost everything else.
+func asn1BitLength(bitString []byte) int {
+	bitLen := len(bitString) * 8
+
+	for i := range bitString {
+		b := bitString[len(bitString)-i-1]
+
+		for bit := uint(0); bit < 8; bit++ {
+			if (b>>bit)&1 == 1 {
+				return bitLen
+			}
+			bitLen--
+		}
+	}
+
+	return 0
+}
+
+var (
+	oidExtensionSubjectKeyId          = []int{2, 5, 29, 14}
+	oidExtensionKeyUsage              = []int{2, 5, 29, 15}
+	oidExtensionExtendedKeyUsage      = []int{2, 5, 29, 37}
+	oidExtensionAuthorityKeyId        = []int{2, 5, 29, 35}
+	oidExtensionBasicConstraints      = []int{2, 5, 29, 19}
+	oidExtensionSubjectAltName        = []int{2, 5, 29, 17}
+	oidExtensionCertificatePolicies   = []int{2, 5, 29, 32}
+	oidExtensionNameConstraints       = []int{2, 5, 29, 30}
+	oidExtensionCRLDistributionPoints = []int{2, 5, 29, 31}
+	oidExtensionAuthorityInfoAccess   = []int{1, 3, 6, 1, 5, 5, 7, 1, 1}
+)
+
+var (
+	oidAuthorityInfoAccessOcsp    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1}
+	oidAuthorityInfoAccessIssuers = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 2}
+)
+
+// oidNotInExtensions returns whether an extension with the given oid exists in
+// extensions.
+func oidInExtensions(oid asn1.ObjectIdentifier, extensions []pkix.Extension) bool {
+	for _, e := range extensions {
+		if e.Id.Equal(oid) {
+			return true
+		}
+	}
+	return false
+}
+
+// marshalSANs marshals a list of addresses into a the contents of an X.509
+// SubjectAlternativeName extension.
+func marshalSANs(dnsNames, emailAddresses []string, ipAddresses []net.IP) (derBytes []byte, err error) {
+	var rawValues []asn1.RawValue
+	for _, name := range dnsNames {
+		rawValues = append(rawValues, asn1.RawValue{Tag: 2, Class: 2, Bytes: []byte(name)})
+	}
+	for _, email := range emailAddresses {
+		rawValues = append(rawValues, asn1.RawValue{Tag: 1, Class: 2, Bytes: []byte(email)})
+	}
+	for _, rawIP := range ipAddresses {
+		// If possible, we always want to encode IPv4 addresses in 4 bytes.
+		ip := rawIP.To4()
+		if ip == nil {
+			ip = rawIP
+		}
+		rawValues = append(rawValues, asn1.RawValue{Tag: 7, Class: 2, Bytes: ip})
+	}
+	return asn1.Marshal(rawValues)
+}
+
+func buildExtensions(template *Certificate) (ret []pkix.Extension, err error) {
+	ret = make([]pkix.Extension, 10 /* maximum number of elements. */)
+	n := 0
+
+	if template.KeyUsage != 0 &&
+		!oidInExtensions(oidExtensionKeyUsage, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionKeyUsage
+		ret[n].Critical = true
+
+		var a [2]byte
+		a[0] = reverseBitsInAByte(byte(template.KeyUsage))
+		a[1] = reverseBitsInAByte(byte(template.KeyUsage >> 8))
+
+		l := 1
+		if a[1] != 0 {
+			l = 2
+		}
+
+		bitString := a[:l]
+		ret[n].Value, err = asn1.Marshal(asn1.BitString{Bytes: bitString, BitLength: asn1BitLength(bitString)})
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.ExtKeyUsage) > 0 || len(template.UnknownExtKeyUsage) > 0) &&
+		!oidInExtensions(oidExtensionExtendedKeyUsage, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionExtendedKeyUsage
+
+		var oids []asn1.ObjectIdentifier
+		for _, u := range template.ExtKeyUsage {
+			if oid, ok := oidFromExtKeyUsage(u); ok {
+				oids = append(oids, oid)
+			} else {
+				panic("internal error")
+			}
+		}
+
+		oids = append(oids, template.UnknownExtKeyUsage...)
+
+		ret[n].Value, err = asn1.Marshal(oids)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if template.BasicConstraintsValid && !oidInExtensions(oidExtensionBasicConstraints, template.ExtraExtensions) {
+		// Leaving MaxPathLen as zero indicates that no maximum path
+		// length is desired, unless MaxPathLenZero is set. A value of
+		// -1 causes encoding/asn1 to omit the value as desired.
+		maxPathLen := template.MaxPathLen
+		if maxPathLen == 0 && !template.MaxPathLenZero {
+			maxPathLen = -1
+		}
+		ret[n].Id = oidExtensionBasicConstraints
+		ret[n].Value, err = asn1.Marshal(basicConstraints{template.IsCA, maxPathLen})
+		ret[n].Critical = true
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.SubjectKeyId) > 0 && !oidInExtensions(oidExtensionSubjectKeyId, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionSubjectKeyId
+		ret[n].Value, err = asn1.Marshal(template.SubjectKeyId)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.AuthorityKeyId) > 0 && !oidInExtensions(oidExtensionAuthorityKeyId, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionAuthorityKeyId
+		ret[n].Value, err = asn1.Marshal(authKeyId{template.AuthorityKeyId})
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.OCSPServer) > 0 || len(template.IssuingCertificateURL) > 0) &&
+		!oidInExtensions(oidExtensionAuthorityInfoAccess, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionAuthorityInfoAccess
+		var aiaValues []authorityInfoAccess
+		for _, name := range template.OCSPServer {
+			aiaValues = append(aiaValues, authorityInfoAccess{
+				Method:   oidAuthorityInfoAccessOcsp,
+				Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
+			})
+		}
+		for _, name := range template.IssuingCertificateURL {
+			aiaValues = append(aiaValues, authorityInfoAccess{
+				Method:   oidAuthorityInfoAccessIssuers,
+				Location: asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)},
+			})
+		}
+		ret[n].Value, err = asn1.Marshal(aiaValues)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0) &&
+		!oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionSubjectAltName
+		ret[n].Value, err = marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.PolicyIdentifiers) > 0 &&
+		!oidInExtensions(oidExtensionCertificatePolicies, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionCertificatePolicies
+		policies := make([]policyInformation, len(template.PolicyIdentifiers))
+		for i, policy := range template.PolicyIdentifiers {
+			policies[i].Policy = policy
+		}
+		ret[n].Value, err = asn1.Marshal(policies)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.PermittedDNSDomains) > 0 &&
+		!oidInExtensions(oidExtensionNameConstraints, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionNameConstraints
+		ret[n].Critical = template.PermittedDNSDomainsCritical
+
+		var out nameConstraints
+		out.Permitted = make([]generalSubtree, len(template.PermittedDNSDomains))
+		for i, permitted := range template.PermittedDNSDomains {
+			out.Permitted[i] = generalSubtree{Name: permitted}
+		}
+		ret[n].Value, err = asn1.Marshal(out)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	if len(template.CRLDistributionPoints) > 0 &&
+		!oidInExtensions(oidExtensionCRLDistributionPoints, template.ExtraExtensions) {
+		ret[n].Id = oidExtensionCRLDistributionPoints
+
+		var crlDp []distributionPoint
+		for _, name := range template.CRLDistributionPoints {
+			rawFullName, _ := asn1.Marshal(asn1.RawValue{Tag: 6, Class: 2, Bytes: []byte(name)})
+
+			dp := distributionPoint{
+				DistributionPoint: distributionPointName{
+					FullName: asn1.RawValue{Tag: 0, Class: 2, IsCompound: true, Bytes: rawFullName},
+				},
+			}
+			crlDp = append(crlDp, dp)
+		}
+
+		ret[n].Value, err = asn1.Marshal(crlDp)
+		if err != nil {
+			return
+		}
+		n++
+	}
+
+	// Adding another extension here? Remember to update the maximum number
+	// of elements in the make() at the top of the function.
+
+	return append(ret[:n], template.ExtraExtensions...), nil
+}
+
+func subjectBytes(cert *Certificate) ([]byte, error) {
+	if len(cert.RawSubject) > 0 {
+		return cert.RawSubject, nil
+	}
+
+	return asn1.Marshal(cert.Subject.ToRDNSequence())
+}
+
+// signingParamsForPublicKey returns the parameters to use for signing with
+// priv. If requestedSigAlgo is not zero then it overrides the default
+// signature algorithm.
+func signingParamsForPublicKey(pub interface{}, requestedSigAlgo SignatureAlgorithm) (hashFunc Hash, sigAlgo pkix.AlgorithmIdentifier, err error) {
+	var pubType PublicKeyAlgorithm
+
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		pubType = RSA
+		hashFunc = SHA256
+		sigAlgo.Algorithm = oidSignatureSHA256WithRSA
+		sigAlgo.Parameters = asn1.RawValue{
+			Tag: 5,
+		}
+
+	case *ecdsa.PublicKey:
+		pubType = ECDSA
+		switch pub.Curve {
+		case elliptic.P224(), elliptic.P256():
+			hashFunc = SHA256
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA256
+		case elliptic.P384():
+			hashFunc = SHA384
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA384
+		case elliptic.P521():
+			hashFunc = SHA512
+			sigAlgo.Algorithm = oidSignatureECDSAWithSHA512
+		default:
+			err = errors.New("x509: unknown elliptic curve")
+		}
+	case *PublicKey:
+		pubType = ECDSA
+		switch pub.Curve {
+		case P256Sm2():
+			hashFunc = SM3
+			sigAlgo.Algorithm = oidSignatureSM2WithSM3
+		default:
+			err = errors.New("x509: unknown SM2 curve")
+		}
+	default:
+		err = errors.New("x509: only RSA and ECDSA keys supported")
+	}
+
+	if err != nil {
+		return
+	}
+
+	if requestedSigAlgo == 0 {
+		return
+	}
+
+	found := false
+	for _, details := range signatureAlgorithmDetails {
+		if details.algo == requestedSigAlgo {
+			if details.pubKeyAlgo != pubType {
+				err = errors.New("x509: requested SignatureAlgorithm does not match private key type")
+				return
+			}
+			sigAlgo.Algorithm, hashFunc = details.oid, details.hash
+			if hashFunc == 0 {
+				err = errors.New("x509: cannot sign with hash function requested")
+				return
+			}
+			if requestedSigAlgo.isRSAPSS() {
+				sigAlgo.Parameters = rsaPSSParameters(hashFunc)
+			}
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		err = errors.New("x509: unknown SignatureAlgorithm")
+	}
+
+	return
+}
+
+// CreateCertificate creates a new certificate based on a template. The
+// following members of template are used: SerialNumber, Subject, NotBefore,
+// NotAfter, KeyUsage, ExtKeyUsage, UnknownExtKeyUsage, BasicConstraintsValid,
+// IsCA, MaxPathLen, SubjectKeyId, DNSNames, PermittedDNSDomainsCritical,
+// PermittedDNSDomains, SignatureAlgorithm.
+//
+// The certificate is signed by parent. If parent is equal to template then the
+// certificate is self-signed. The parameter pub is the public key of the
+// signee and priv is the private key of the signer.
+//
+// The returned slice is the certificate in DER encoding.
+//
+// All keys types that are implemented via crypto.Signer are supported (This
+// includes *rsa.PublicKey and *ecdsa.PublicKey.)
+func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv interface{}) (cert []byte, err error) {
+	key, ok := priv.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
+	}
+
+	if template.SerialNumber == nil {
+		return nil, errors.New("x509: no SerialNumber given")
+	}
+
+	hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
+	if err != nil {
+		return nil, err
+	}
+
+	publicKeyBytes, publicKeyAlgorithm, err := marshalPublicKey(pub)
+	if err != nil {
+		return nil, err
+	}
+
+	asn1Issuer, err := subjectBytes(parent)
+	if err != nil {
+		return
+	}
+
+	asn1Subject, err := subjectBytes(template)
+	if err != nil {
+		return
+	}
+
+	if !bytes.Equal(asn1Issuer, asn1Subject) && len(parent.SubjectKeyId) > 0 {
+		template.AuthorityKeyId = parent.SubjectKeyId
+	}
+
+	extensions, err := buildExtensions(template)
+	if err != nil {
+		return
+	}
+	encodedPublicKey := asn1.BitString{BitLength: len(publicKeyBytes) * 8, Bytes: publicKeyBytes}
+	c := tbsCertificate{
+		Version:            2,
+		SerialNumber:       template.SerialNumber,
+		SignatureAlgorithm: signatureAlgorithm,
+		Issuer:             asn1.RawValue{FullBytes: asn1Issuer},
+		Validity:           validity{template.NotBefore.UTC(), template.NotAfter.UTC()},
+		Subject:            asn1.RawValue{FullBytes: asn1Subject},
+		PublicKey:          publicKeyInfo{nil, publicKeyAlgorithm, encodedPublicKey},
+		Extensions:         extensions,
+	}
+
+	tbsCertContents, err := asn1.Marshal(c)
+	if err != nil {
+		return
+	}
+
+	c.Raw = tbsCertContents
+
+	h := hashFunc.New()
+	h.Write(tbsCertContents)
+	digest := h.Sum(nil)
+
+	var signerOpts crypto.SignerOpts
+	signerOpts = hashFunc
+	if template.SignatureAlgorithm != 0 && template.SignatureAlgorithm.isRSAPSS() {
+		signerOpts = &rsa.PSSOptions{
+			SaltLength: rsa.PSSSaltLengthEqualsHash,
+			Hash:       crypto.Hash(hashFunc),
+		}
+	}
+
+	var signature []byte
+	signature, err = key.Sign(rand, digest, signerOpts)
+	if err != nil {
+		return
+	}
+
+	return asn1.Marshal(certificate{
+		nil,
+		c,
+		signatureAlgorithm,
+		asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
+	})
+}
+
+// pemCRLPrefix is the magic string that indicates that we have a PEM encoded
+// CRL.
+var pemCRLPrefix = []byte("-----BEGIN X509 CRL")
+
+// pemType is the type of a PEM encoded CRL.
+var pemType = "X509 CRL"
+
+// ParseCRL parses a CRL from the given bytes. It's often the case that PEM
+// encoded CRLs will appear where they should be DER encoded, so this function
+// will transparently handle PEM encoding as long as there isn't any leading
+// garbage.
+func ParseCRL(crlBytes []byte) (*pkix.CertificateList, error) {
+	if bytes.HasPrefix(crlBytes, pemCRLPrefix) {
+		block, _ := pem.Decode(crlBytes)
+		if block != nil && block.Type == pemType {
+			crlBytes = block.Bytes
+		}
+	}
+	return ParseDERCRL(crlBytes)
+}
+
+// ParseDERCRL parses a DER encoded CRL from the given bytes.
+func ParseDERCRL(derBytes []byte) (*pkix.CertificateList, error) {
+	certList := new(pkix.CertificateList)
+	if rest, err := asn1.Unmarshal(derBytes, certList); err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after CRL")
+	}
+	return certList, nil
+}
+
+// CreateCRL returns a DER encoded CRL, signed by this Certificate, that
+// contains the given list of revoked certificates.
+func (c *Certificate) CreateCRL(rand io.Reader, priv interface{}, revokedCerts []pkix.RevokedCertificate, now, expiry time.Time) (crlBytes []byte, err error) {
+	key, ok := priv.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
+	}
+
+	hashFunc, signatureAlgorithm, err := signingParamsForPublicKey(key.Public(), 0)
+	if err != nil {
+		return nil, err
+	}
+
+	// Force revocation times to UTC per RFC 5280.
+	revokedCertsUTC := make([]pkix.RevokedCertificate, len(revokedCerts))
+	for i, rc := range revokedCerts {
+		rc.RevocationTime = rc.RevocationTime.UTC()
+		revokedCertsUTC[i] = rc
+	}
+
+	tbsCertList := pkix.TBSCertificateList{
+		Version:             1,
+		Signature:           signatureAlgorithm,
+		Issuer:              c.Subject.ToRDNSequence(),
+		ThisUpdate:          now.UTC(),
+		NextUpdate:          expiry.UTC(),
+		RevokedCertificates: revokedCertsUTC,
+	}
+
+	// Authority Key Id
+	if len(c.SubjectKeyId) > 0 {
+		var aki pkix.Extension
+		aki.Id = oidExtensionAuthorityKeyId
+		aki.Value, err = asn1.Marshal(authKeyId{Id: c.SubjectKeyId})
+		if err != nil {
+			return
+		}
+		tbsCertList.Extensions = append(tbsCertList.Extensions, aki)
+	}
+
+	tbsCertListContents, err := asn1.Marshal(tbsCertList)
+	if err != nil {
+		return
+	}
+
+	h := hashFunc.New()
+	h.Write(tbsCertListContents)
+	digest := h.Sum(nil)
+
+	var signature []byte
+	signature, err = key.Sign(rand, digest, hashFunc)
+	if err != nil {
+		return
+	}
+
+	return asn1.Marshal(pkix.CertificateList{
+		TBSCertList:        tbsCertList,
+		SignatureAlgorithm: signatureAlgorithm,
+		SignatureValue:     asn1.BitString{Bytes: signature, BitLength: len(signature) * 8},
+	})
+}
+
+// CertificateRequest represents a PKCS #10, certificate signature request.
+type CertificateRequest struct {
+	Raw                      []byte // Complete ASN.1 DER content (CSR, signature algorithm and signature).
+	RawTBSCertificateRequest []byte // Certificate request info part of raw ASN.1 DER content.
+	RawSubjectPublicKeyInfo  []byte // DER encoded SubjectPublicKeyInfo.
+	RawSubject               []byte // DER encoded Subject.
+
+	Version            int
+	Signature          []byte
+	SignatureAlgorithm SignatureAlgorithm
+
+	PublicKeyAlgorithm PublicKeyAlgorithm
+	PublicKey          interface{}
+
+	Subject pkix.Name
+
+	// Attributes is the dried husk of a bug and shouldn't be used.
+	Attributes []pkix.AttributeTypeAndValueSET
+
+	// Extensions contains raw X.509 extensions. When parsing CSRs, this
+	// can be used to extract extensions that are not parsed by this
+	// package.
+	Extensions []pkix.Extension
+
+	// ExtraExtensions contains extensions to be copied, raw, into any
+	// marshaled CSR. Values override any extensions that would otherwise
+	// be produced based on the other fields but are overridden by any
+	// extensions specified in Attributes.
+	//
+	// The ExtraExtensions field is not populated when parsing CSRs, see
+	// Extensions.
+	ExtraExtensions []pkix.Extension
+
+	// Subject Alternate Name values.
+	DNSNames       []string
+	EmailAddresses []string
+	IPAddresses    []net.IP
+}
+
+// These structures reflect the ASN.1 structure of X.509 certificate
+// signature requests (see RFC 2986):
+
+type tbsCertificateRequest struct {
+	Raw           asn1.RawContent
+	Version       int
+	Subject       asn1.RawValue
+	PublicKey     publicKeyInfo
+	RawAttributes []asn1.RawValue `asn1:"tag:0"`
+}
+
+type certificateRequest struct {
+	Raw                asn1.RawContent
+	TBSCSR             tbsCertificateRequest
+	SignatureAlgorithm pkix.AlgorithmIdentifier
+	SignatureValue     asn1.BitString
+}
+
+// oidExtensionRequest is a PKCS#9 OBJECT IDENTIFIER that indicates requested
+// extensions in a CSR.
+var oidExtensionRequest = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 14}
+
+// newRawAttributes converts AttributeTypeAndValueSETs from a template
+// CertificateRequest's Attributes into tbsCertificateRequest RawAttributes.
+func newRawAttributes(attributes []pkix.AttributeTypeAndValueSET) ([]asn1.RawValue, error) {
+	var rawAttributes []asn1.RawValue
+	b, err := asn1.Marshal(attributes)
+	if err != nil {
+		return nil, err
+	}
+	rest, err := asn1.Unmarshal(b, &rawAttributes)
+	if err != nil {
+		return nil, err
+	}
+	if len(rest) != 0 {
+		return nil, errors.New("x509: failed to unmarshal raw CSR Attributes")
+	}
+	return rawAttributes, nil
+}
+
+// parseRawAttributes Unmarshals RawAttributes intos AttributeTypeAndValueSETs.
+func parseRawAttributes(rawAttributes []asn1.RawValue) []pkix.AttributeTypeAndValueSET {
+	var attributes []pkix.AttributeTypeAndValueSET
+	for _, rawAttr := range rawAttributes {
+		var attr pkix.AttributeTypeAndValueSET
+		rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr)
+		// Ignore attributes that don't parse into pkix.AttributeTypeAndValueSET
+		// (i.e.: challengePassword or unstructuredName).
+		if err == nil && len(rest) == 0 {
+			attributes = append(attributes, attr)
+		}
+	}
+	return attributes
+}
+
+// parseCSRExtensions parses the attributes from a CSR and extracts any
+// requested extensions.
+func parseCSRExtensions(rawAttributes []asn1.RawValue) ([]pkix.Extension, error) {
+	// pkcs10Attribute reflects the Attribute structure from section 4.1 of
+	// https://tools.ietf.org/html/rfc2986.
+	type pkcs10Attribute struct {
+		Id     asn1.ObjectIdentifier
+		Values []asn1.RawValue `asn1:"set"`
+	}
+
+	var ret []pkix.Extension
+	for _, rawAttr := range rawAttributes {
+		var attr pkcs10Attribute
+		if rest, err := asn1.Unmarshal(rawAttr.FullBytes, &attr); err != nil || len(rest) != 0 || len(attr.Values) == 0 {
+			// Ignore attributes that don't parse.
+			continue
+		}
+
+		if !attr.Id.Equal(oidExtensionRequest) {
+			continue
+		}
+
+		var extensions []pkix.Extension
+		if _, err := asn1.Unmarshal(attr.Values[0].FullBytes, &extensions); err != nil {
+			return nil, err
+		}
+		ret = append(ret, extensions...)
+	}
+
+	return ret, nil
+}
+
+// CreateCertificateRequest creates a new certificate request based on a template.
+// The following members of template are used: Subject, Attributes,
+// SignatureAlgorithm, Extensions, DNSNames, EmailAddresses, and IPAddresses.
+// The private key is the private key of the signer.
+//
+// The returned slice is the certificate request in DER encoding.
+//
+// All keys types that are implemented via crypto.Signer are supported (This
+// includes *rsa.PublicKey and *ecdsa.PublicKey.)
+func CreateCertificateRequest(rand io.Reader, template *CertificateRequest, priv interface{}) (csr []byte, err error) {
+	key, ok := priv.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("x509: certificate private key does not implement crypto.Signer")
+	}
+
+	var hashFunc Hash
+	var sigAlgo pkix.AlgorithmIdentifier
+	hashFunc, sigAlgo, err = signingParamsForPublicKey(key.Public(), template.SignatureAlgorithm)
+	if err != nil {
+		return nil, err
+	}
+
+	var publicKeyBytes []byte
+	var publicKeyAlgorithm pkix.AlgorithmIdentifier
+	publicKeyBytes, publicKeyAlgorithm, err = marshalPublicKey(key.Public())
+	if err != nil {
+		return nil, err
+	}
+
+	var extensions []pkix.Extension
+
+	if (len(template.DNSNames) > 0 || len(template.EmailAddresses) > 0 || len(template.IPAddresses) > 0) &&
+		!oidInExtensions(oidExtensionSubjectAltName, template.ExtraExtensions) {
+		sanBytes, err := marshalSANs(template.DNSNames, template.EmailAddresses, template.IPAddresses)
+		if err != nil {
+			return nil, err
+		}
+
+		extensions = append(extensions, pkix.Extension{
+			Id:    oidExtensionSubjectAltName,
+			Value: sanBytes,
+		})
+	}
+
+	extensions = append(extensions, template.ExtraExtensions...)
+
+	var attributes []pkix.AttributeTypeAndValueSET
+	attributes = append(attributes, template.Attributes...)
+
+	if len(extensions) > 0 {
+		// specifiedExtensions contains all the extensions that we
+		// found specified via template.Attributes.
+		specifiedExtensions := make(map[string]bool)
+
+		for _, atvSet := range template.Attributes {
+			if !atvSet.Type.Equal(oidExtensionRequest) {
+				continue
+			}
+
+			for _, atvs := range atvSet.Value {
+				for _, atv := range atvs {
+					specifiedExtensions[atv.Type.String()] = true
+				}
+			}
+		}
+
+		atvs := make([]pkix.AttributeTypeAndValue, 0, len(extensions))
+		for _, e := range extensions {
+			if specifiedExtensions[e.Id.String()] {
+				// Attributes already contained a value for
+				// this extension and it takes priority.
+				continue
+			}
+
+			atvs = append(atvs, pkix.AttributeTypeAndValue{
+				// There is no place for the critical flag in a CSR.
+				Type:  e.Id,
+				Value: e.Value,
+			})
+		}
+
+		// Append the extensions to an existing attribute if possible.
+		appended := false
+		for _, atvSet := range attributes {
+			if !atvSet.Type.Equal(oidExtensionRequest) || len(atvSet.Value) == 0 {
+				continue
+			}
+
+			atvSet.Value[0] = append(atvSet.Value[0], atvs...)
+			appended = true
+			break
+		}
+
+		// Otherwise, add a new attribute for the extensions.
+		if !appended {
+			attributes = append(attributes, pkix.AttributeTypeAndValueSET{
+				Type: oidExtensionRequest,
+				Value: [][]pkix.AttributeTypeAndValue{
+					atvs,
+				},
+			})
+		}
+	}
+
+	asn1Subject := template.RawSubject
+	if len(asn1Subject) == 0 {
+		asn1Subject, err = asn1.Marshal(template.Subject.ToRDNSequence())
+		if err != nil {
+			return
+		}
+	}
+
+	rawAttributes, err := newRawAttributes(attributes)
+	if err != nil {
+		return
+	}
+
+	tbsCSR := tbsCertificateRequest{
+		Version: 0, // PKCS #10, RFC 2986
+		Subject: asn1.RawValue{FullBytes: asn1Subject},
+		PublicKey: publicKeyInfo{
+			Algorithm: publicKeyAlgorithm,
+			PublicKey: asn1.BitString{
+				Bytes:     publicKeyBytes,
+				BitLength: len(publicKeyBytes) * 8,
+			},
+		},
+		RawAttributes: rawAttributes,
+	}
+
+	tbsCSRContents, err := asn1.Marshal(tbsCSR)
+	if err != nil {
+		return
+	}
+	tbsCSR.Raw = tbsCSRContents
+
+	h := hashFunc.New()
+	h.Write(tbsCSRContents)
+	digest := h.Sum(nil)
+
+	var signature []byte
+	signature, err = key.Sign(rand, digest, hashFunc)
+	if err != nil {
+		return
+	}
+
+	return asn1.Marshal(certificateRequest{
+		TBSCSR:             tbsCSR,
+		SignatureAlgorithm: sigAlgo,
+		SignatureValue: asn1.BitString{
+			Bytes:     signature,
+			BitLength: len(signature) * 8,
+		},
+	})
+}
+
+// ParseCertificateRequest parses a single certificate request from the
+// given ASN.1 DER data.
+func ParseCertificateRequest(asn1Data []byte) (*CertificateRequest, error) {
+	var csr certificateRequest
+
+	rest, err := asn1.Unmarshal(asn1Data, &csr)
+	if err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, asn1.SyntaxError{Msg: "trailing data"}
+	}
+
+	return parseCertificateRequest(&csr)
+}
+
+func parseCertificateRequest(in *certificateRequest) (*CertificateRequest, error) {
+	out := &CertificateRequest{
+		Raw: in.Raw,
+		RawTBSCertificateRequest: in.TBSCSR.Raw,
+		RawSubjectPublicKeyInfo:  in.TBSCSR.PublicKey.Raw,
+		RawSubject:               in.TBSCSR.Subject.FullBytes,
+
+		Signature:          in.SignatureValue.RightAlign(),
+		SignatureAlgorithm: getSignatureAlgorithmFromAI(in.SignatureAlgorithm),
+
+		PublicKeyAlgorithm: getPublicKeyAlgorithmFromOID(in.TBSCSR.PublicKey.Algorithm.Algorithm),
+
+		Version:    in.TBSCSR.Version,
+		Attributes: parseRawAttributes(in.TBSCSR.RawAttributes),
+	}
+
+	var err error
+	out.PublicKey, err = parsePublicKey(out.PublicKeyAlgorithm, &in.TBSCSR.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+
+	var subject pkix.RDNSequence
+	if rest, err := asn1.Unmarshal(in.TBSCSR.Subject.FullBytes, &subject); err != nil {
+		return nil, err
+	} else if len(rest) != 0 {
+		return nil, errors.New("x509: trailing data after X.509 Subject")
+	}
+
+	out.Subject.FillFromRDNSequence(&subject)
+
+	if out.Extensions, err = parseCSRExtensions(in.TBSCSR.RawAttributes); err != nil {
+		return nil, err
+	}
+
+	for _, extension := range out.Extensions {
+		if extension.Id.Equal(oidExtensionSubjectAltName) {
+			out.DNSNames, out.EmailAddresses, out.IPAddresses, err = parseSANExtension(extension.Value)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return out, nil
+}
+
+// CheckSignature reports whether the signature on c is valid.
+func (c *CertificateRequest) CheckSignature() error {
+	return checkSignature(c.SignatureAlgorithm, c.RawTBSCertificateRequest, c.Signature, c.PublicKey)
+}
+
+func ReadCertificateRequestFromMem(data []byte) (*CertificateRequest, error) {
+	block, _ := pem.Decode(data)
+	if block == nil {
+		return nil, errors.New("failed to decode certificate request")
+	}
+	return ParseCertificateRequest(block.Bytes)
+}
+
+func ReadCertificateRequestFromPem(FileName string) (*CertificateRequest, error) {
+	data, err := ioutil.ReadFile(FileName)
+	if err != nil {
+		return nil, err
+	}
+	return ReadCertificateRequestFromMem(data)
+}
+
+func CreateCertificateRequestToMem(template *CertificateRequest, privKey *PrivateKey) ([]byte, error) {
+	der, err := CreateCertificateRequest(rand.Reader, template, privKey)
+	if err != nil {
+		return nil, err
+	}
+	block := &pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: der,
+	}
+	return pem.EncodeToMemory(block), nil
+}
+
+func CreateCertificateRequestToPem(FileName string, template *CertificateRequest,
+	privKey *PrivateKey) (bool, error) {
+	der, err := CreateCertificateRequest(rand.Reader, template, privKey)
+	if err != nil {
+		return false, err
+	}
+	block := &pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: der,
+	}
+	file, err := os.Create(FileName)
+	if err != nil {
+		return false, err
+	}
+	defer file.Close()
+	err = pem.Encode(file, block)
+	if err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+func ReadCertificateFromMem(data []byte) (*Certificate, error) {
+	block, _ := pem.Decode(data)
+	if block == nil {
+		return nil, errors.New("failed to decode certificate request")
+	}
+	return ParseCertificate(block.Bytes)
+}
+
+func ReadCertificateFromPem(FileName string) (*Certificate, error) {
+	data, err := ioutil.ReadFile(FileName)
+	if err != nil {
+		return nil, err
+	}
+	return ReadCertificateFromMem(data)
+}
+
+func CreateCertificateToMem(template, parent *Certificate, pubKey *PublicKey, privKey *PrivateKey) ([]byte, error) {
+	der, err := CreateCertificate(rand.Reader, template, parent, pubKey, privKey)
+	if err != nil {
+		return nil, err
+	}
+	block := &pem.Block{
+		Type:  "CERTIFICATE",
+		Bytes: der,
+	}
+	return pem.EncodeToMemory(block), nil
+}
+
+func CreateCertificateToPem(FileName string, template, parent *Certificate, pubKey *PublicKey, privKey *PrivateKey) (bool, error) {
+	der, err := CreateCertificate(rand.Reader, template, parent, pubKey, privKey)
+	if err != nil {
+		return false, err
+	}
+	block := &pem.Block{
+		Type:  "CERTIFICATE",
+		Bytes: der,
+	}
+	file, err := os.Create(FileName)
+	if err != nil {
+		return false, err
+	}
+	defer file.Close()
+	err = pem.Encode(file, block)
+	if err != nil {
+		return false, err
+	}
+	return true, nil
+}
diff --git a/crypto/sm3/sm3_test.go b/crypto/sm3/sm3_test.go
index fe1d1c60..428bcc24 100644
--- a/crypto/sm3/sm3_test.go
+++ b/crypto/sm3/sm3_test.go
@@ -45,6 +45,7 @@ func TestSm3(t *testing.T) {
 	hw.Write(msg)
 	hash := hw.Sum(nil)
 	fmt.Println(hash)
+	fmt.Printf("hash = %d\n", len(hash))
 	fmt.Printf("%s\n", byteToString(hash))
 	hash1 := Sm3Sum(msg)
 	fmt.Println(hash1)
-- 
2.11.0