--- /dev/null
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package ed25519 implements the Ed25519 signature algorithm. See
+// https://ed25519.cr.yp.to/.
+//
+// These functions are also compatible with the “Ed25519” function defined in
+// https://tools.ietf.org/html/draft-irtf-cfrg-eddsa-05.
+package ed25519
+
+// This code is a port of the public domain, “ref10” implementation of ed25519
+// from SUPERCOP.
+
+import (
+ "crypto"
+ cryptorand "crypto/rand"
+ "crypto/sha512"
+ "crypto/subtle"
+ "errors"
+ "io"
+ "strconv"
+
+ "golang.org/x/crypto/ed25519/internal/edwards25519"
+)
+
+const (
+ // PublicKeySize is the size, in bytes, of public keys as used in this package.
+ PublicKeySize = 32
+ // PrivateKeySize is the size, in bytes, of private keys as used in this package.
+ PrivateKeySize = 64
+ // SignatureSize is the size, in bytes, of signatures generated and verified by this package.
+ SignatureSize = 64
+)
+
+// PublicKey is the type of Ed25519 public keys.
+type PublicKey []byte
+
+// PrivateKey is the type of Ed25519 private keys. It implements crypto.Signer.
+type PrivateKey []byte
+
+// Public returns the PublicKey corresponding to priv.
+func (priv PrivateKey) Public() crypto.PublicKey {
+ publicKey := make([]byte, PublicKeySize)
+ copy(publicKey, priv[32:])
+ return PublicKey(publicKey)
+}
+
+// Sign signs the given message with priv.
+// Ed25519 performs two passes over messages to be signed and therefore cannot
+// handle pre-hashed messages. Thus opts.HashFunc() must return zero to
+// indicate the message hasn't been hashed. This can be achieved by passing
+// crypto.Hash(0) as the value for opts.
+func (priv PrivateKey) Sign(rand io.Reader, message []byte, opts crypto.SignerOpts) (signature []byte, err error) {
+ if opts.HashFunc() != crypto.Hash(0) {
+ return nil, errors.New("ed25519: cannot sign hashed message")
+ }
+
+ return Sign(priv, message), nil
+}
+
+// GenerateKey generates a public/private key pair using entropy from rand.
+// If rand is nil, crypto/rand.Reader will be used.
+func GenerateKey(rand io.Reader) (publicKey PublicKey, privateKey PrivateKey, err error) {
+ if rand == nil {
+ rand = cryptorand.Reader
+ }
+
+ privateKey = make([]byte, PrivateKeySize)
+ publicKey = make([]byte, PublicKeySize)
+ _, err = io.ReadFull(rand, privateKey[:32])
+ if err != nil {
+ return nil, nil, err
+ }
+
+ digest := sha512.Sum512(privateKey[:32])
+ digest[0] &= 248
+ digest[31] &= 127
+ digest[31] |= 64
+
+ var A edwards25519.ExtendedGroupElement
+ var hBytes [32]byte
+ copy(hBytes[:], digest[:])
+ edwards25519.GeScalarMultBase(&A, &hBytes)
+ var publicKeyBytes [32]byte
+ A.ToBytes(&publicKeyBytes)
+
+ copy(privateKey[32:], publicKeyBytes[:])
+ copy(publicKey, publicKeyBytes[:])
+
+ return publicKey, privateKey, nil
+}
+
+// Sign signs the message with privateKey and returns a signature. It will
+// panic if len(privateKey) is not PrivateKeySize.
+func Sign(privateKey PrivateKey, message []byte) []byte {
+ if l := len(privateKey); l != PrivateKeySize {
+ panic("ed25519: bad private key length: " + strconv.Itoa(l))
+ }
+
+ h := sha512.New()
+ h.Write(privateKey[:32])
+
+ var digest1, messageDigest, hramDigest [64]byte
+ var expandedSecretKey [32]byte
+ h.Sum(digest1[:0])
+ copy(expandedSecretKey[:], digest1[:])
+ expandedSecretKey[0] &= 248
+ expandedSecretKey[31] &= 63
+ expandedSecretKey[31] |= 64
+
+ h.Reset()
+ h.Write(digest1[32:])
+ h.Write(message)
+ h.Sum(messageDigest[:0])
+
+ var messageDigestReduced [32]byte
+ edwards25519.ScReduce(&messageDigestReduced, &messageDigest)
+ var R edwards25519.ExtendedGroupElement
+ edwards25519.GeScalarMultBase(&R, &messageDigestReduced)
+
+ var encodedR [32]byte
+ R.ToBytes(&encodedR)
+
+ h.Reset()
+ h.Write(encodedR[:])
+ h.Write(privateKey[32:])
+ h.Write(message)
+ h.Sum(hramDigest[:0])
+ var hramDigestReduced [32]byte
+ edwards25519.ScReduce(&hramDigestReduced, &hramDigest)
+
+ var s [32]byte
+ edwards25519.ScMulAdd(&s, &hramDigestReduced, &expandedSecretKey, &messageDigestReduced)
+
+ signature := make([]byte, SignatureSize)
+ copy(signature[:], encodedR[:])
+ copy(signature[32:], s[:])
+
+ return signature
+}
+
+// Verify reports whether sig is a valid signature of message by publicKey. It
+// will panic if len(publicKey) is not PublicKeySize.
+func Verify(publicKey PublicKey, message, sig []byte) bool {
+ if l := len(publicKey); l != PublicKeySize {
+ panic("ed25519: bad public key length: " + strconv.Itoa(l))
+ }
+
+ if len(sig) != SignatureSize || sig[63]&224 != 0 {
+ return false
+ }
+
+ var A edwards25519.ExtendedGroupElement
+ var publicKeyBytes [32]byte
+ copy(publicKeyBytes[:], publicKey)
+ if !A.FromBytes(&publicKeyBytes) {
+ return false
+ }
+ edwards25519.FeNeg(&A.X, &A.X)
+ edwards25519.FeNeg(&A.T, &A.T)
+
+ h := sha512.New()
+ h.Write(sig[:32])
+ h.Write(publicKey[:])
+ h.Write(message)
+ var digest [64]byte
+ h.Sum(digest[:0])
+
+ var hReduced [32]byte
+ edwards25519.ScReduce(&hReduced, &digest)
+
+ var R edwards25519.ProjectiveGroupElement
+ var b [32]byte
+ copy(b[:], sig[32:])
+ edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &b)
+
+ var checkR [32]byte
+ R.ToBytes(&checkR)
+ return subtle.ConstantTimeCompare(sig[:32], checkR[:]) == 1
+}
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