diff options
Diffstat (limited to 'vendor/github.com/keybase/go-crypto/ed25519/ed25519.go')
| -rw-r--r-- | vendor/github.com/keybase/go-crypto/ed25519/ed25519.go | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/vendor/github.com/keybase/go-crypto/ed25519/ed25519.go b/vendor/github.com/keybase/go-crypto/ed25519/ed25519.go new file mode 100644 index 0000000000..9c7a888076 --- /dev/null +++ b/vendor/github.com/keybase/go-crypto/ed25519/ed25519.go @@ -0,0 +1,181 @@ +// 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 +// http://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" + + "github.com/keybase/go-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 +} |