Merge pull request #201 from Bytom/v0.1

[bytom/vapor.git] / vendor / github.com / bytom / crypto / ed25519 / chainkd / expanded_key.go

diff --git a/vendor/github.com/bytom/crypto/ed25519/chainkd/expanded_key.go b/vendor/github.com/bytom/crypto/ed25519/chainkd/expanded_key.go
new file mode 100644 (file)
index 0000000..fbc5db1
--- /dev/null
+++ b/vendor/github.com/bytom/crypto/ed25519/chainkd/expanded_key.go
@@ -0,0 +1,102 @@
+// Package chainkd This is an extension to ed25519.Sign that is compatible with NaCl `crypto_sign`
+// function taking 64-byte expanded private key (where the left part is a pre-multiplied
+// scalar and the right part is "prefix" used for generating a nonce).
+//
+// Invariants:
+// 1) Expanded(PrivateKey).Sign() == PrivateKey.Sign()
+// 2) InnerSign(Expanded(PrivateKey)) == Sign(PrivateKey)
+package chainkd
+
+import (
+       "crypto"
+       "crypto/sha512"
+       "errors"
+       "io"
+       "strconv"
+
+       "github.com/bytom/crypto/ed25519"
+       "github.com/bytom/crypto/ed25519/internal/edwards25519"
+)
+
+const (
+       // ExpandedPrivateKeySize is the size, in bytes, of a "secret key" as defined in NaCl.
+       ExpandedPrivateKeySize = 64
+)
+
+// ExpandedPrivateKey is the type of NaCl secret keys. It implements crypto.Signer.
+type ExpandedPrivateKey []byte
+
+// Public returns the PublicKey corresponding to secret key.
+func (priv ExpandedPrivateKey) Public() crypto.PublicKey {
+       var A edwards25519.ExtendedGroupElement
+       var scalar [32]byte
+       copy(scalar[:], priv[:32])
+       edwards25519.GeScalarMultBase(&A, &scalar)
+       var publicKeyBytes [32]byte
+       A.ToBytes(&publicKeyBytes)
+       return ed25519.PublicKey(publicKeyBytes[:])
+}
+
+func expandEd25519PrivateKey(priv ed25519.PrivateKey) ExpandedPrivateKey {
+       digest := sha512.Sum512(priv[:32])
+       digest[0] &= 248
+       digest[31] &= 127
+       digest[31] |= 64
+       return ExpandedPrivateKey(digest[:])
+}
+
+// Sign signs the given message with expanded private key.
+// 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 ExpandedPrivateKey) 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 Ed25519InnerSign(priv, message), nil
+}
+
+// Ed25519InnerSign signs the message with expanded private key and returns a signature.
+// It will panic if len(privateKey) is not ExpandedPrivateKeySize.
+func Ed25519InnerSign(privateKey ExpandedPrivateKey, message []byte) []byte {
+       if l := len(privateKey); l != ExpandedPrivateKeySize {
+               panic("ed25519: bad private key length: " + strconv.Itoa(l))
+       }
+
+       var messageDigest, hramDigest [64]byte
+
+       h := sha512.New()
+       h.Write(privateKey[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)
+
+       publicKey := privateKey.Public().(ed25519.PublicKey)
+       h.Reset()
+       h.Write(encodedR[:])
+       h.Write(publicKey[:])
+       h.Write(message)
+       h.Sum(hramDigest[:0])
+       var hramDigestReduced [32]byte
+       edwards25519.ScReduce(&hramDigestReduced, &hramDigest)
+
+       var sk [32]byte
+       copy(sk[:], privateKey[:32])
+       var s [32]byte
+       edwards25519.ScMulAdd(&s, &hramDigestReduced, &sk, &messageDigestReduced)
+
+       signature := make([]byte, ed25519.SignatureSize)
+       copy(signature[:], encodedR[:])
+       copy(signature[32:], s[:])
+
+       return signature
+}