src/crypto/ed25519/ed25519.go - go - Git at Google

 // 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
 // RFC 8032. However, unlike RFC 8032's formulation, this package's private key
 // representation includes a public key suffix to make multiple signing
 // operations with the same key more efficient. This package refers to the RFC
 // 8032 private key as the “seed”.
 package ed25519

 // This code is a port of the public domain, “ref10” implementation of ed25519
 // from SUPERCOP.

 import (
 	"bytes"
 	"crypto"
 	"crypto/ed25519/internal/edwards25519"
 	cryptorand "crypto/rand"
 	"crypto/sha512"
 	"errors"
 	"io"
 	"strconv"
 )

 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
 	// SeedSize is the size, in bytes, of private key seeds. These are the private key representations used by RFC 8032.
 	SeedSize = 32
 )

 // PublicKey is the type of Ed25519 public keys.
 type PublicKey []byte

 // Equal reports whether pub and x have the same value.
 func (pub PublicKey) Equal(x crypto.PublicKey) bool {
 	xx, ok := x.(PublicKey)
 	if !ok {
 		return false
 	}
 	return bytes.Equal(pub, xx)
 }

 // 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)
 }

 // Seed returns the private key seed corresponding to priv. It is provided for
 // interoperability with RFC 8032. RFC 8032's private keys correspond to seeds
 // in this package.
 func (priv PrivateKey) Seed() []byte {
 	seed := make([]byte, SeedSize)
 	copy(seed, priv[:32])
 	return seed
 }

 // 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, PrivateKey, error) {
 	if rand == nil {
 		rand = cryptorand.Reader
 	}

 	seed := make([]byte, SeedSize)
 	if _, err := io.ReadFull(rand, seed); err != nil {
 		return nil, nil, err
 	}

 	privateKey := NewKeyFromSeed(seed)
 	publicKey := make([]byte, PublicKeySize)
 	copy(publicKey, privateKey[32:])

 	return publicKey, privateKey, nil
 }

 // NewKeyFromSeed calculates a private key from a seed. It will panic if
 // len(seed) is not SeedSize. This function is provided for interoperability
 // with RFC 8032. RFC 8032's private keys correspond to seeds in this
 // package.
 func NewKeyFromSeed(seed []byte) PrivateKey {
 	// Outline the function body so that the returned key can be stack-allocated.
 	privateKey := make([]byte, PrivateKeySize)
 	newKeyFromSeed(privateKey, seed)
 	return privateKey
 }

 func newKeyFromSeed(privateKey, seed []byte) {
 	if l := len(seed); l != SeedSize {
 		panic("ed25519: bad seed length: " + strconv.Itoa(l))
 	}

 	digest := sha512.Sum512(seed)
 	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, seed)
 	copy(privateKey[32:], publicKeyBytes[:])
 }

 // 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 {
 	// Outline the function body so that the returned signature can be
 	// stack-allocated.
 	signature := make([]byte, SignatureSize)
 	sign(signature, privateKey, message)
 	return signature
 }

 func signGeneric(signature, privateKey, message []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)

 	copy(signature[:], encodedR[:])
 	copy(signature[32:], s[:])
 }

 // 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 {
 	return verify(publicKey, message, sig)
 }

 func verifyGeneric(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 s [32]byte
 	copy(s[:], sig[32:])

 	// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
 	// the range [0, order) in order to prevent signature malleability.
 	if !edwards25519.ScMinimal(&s) {
 		return false
 	}

 	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &s)

 	var checkR [32]byte
 	R.ToBytes(&checkR)
 	return bytes.Equal(sig[:32], checkR[:])
 }
	// 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
	// RFC 8032. However, unlike RFC 8032's formulation, this package's private key
	// representation includes a public key suffix to make multiple signing
	// operations with the same key more efficient. This package refers to the RFC
	// 8032 private key as the “seed”.
	package ed25519

	// This code is a port of the public domain, “ref10” implementation of ed25519
	// from SUPERCOP.

	import (
	"bytes"
	"crypto"
	"crypto/ed25519/internal/edwards25519"
	cryptorand "crypto/rand"
	"crypto/sha512"
	"errors"
	"io"
	"strconv"
	)

	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
	// SeedSize is the size, in bytes, of private key seeds. These are the private key representations used by RFC 8032.
	SeedSize = 32
	)

	// PublicKey is the type of Ed25519 public keys.
	type PublicKey []byte

	// Equal reports whether pub and x have the same value.
	func (pub PublicKey) Equal(x crypto.PublicKey) bool {
	xx, ok := x.(PublicKey)
	if !ok {
	return false
	}
	return bytes.Equal(pub, xx)
	}

	// 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)
	}

	// Seed returns the private key seed corresponding to priv. It is provided for
	// interoperability with RFC 8032. RFC 8032's private keys correspond to seeds
	// in this package.
	func (priv PrivateKey) Seed() []byte {
	seed := make([]byte, SeedSize)
	copy(seed, priv[:32])
	return seed
	}

	// 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, PrivateKey, error) {
	if rand == nil {
	rand = cryptorand.Reader
	}

	seed := make([]byte, SeedSize)
	if _, err := io.ReadFull(rand, seed); err != nil {
	return nil, nil, err
	}

	privateKey := NewKeyFromSeed(seed)
	publicKey := make([]byte, PublicKeySize)
	copy(publicKey, privateKey[32:])

	return publicKey, privateKey, nil
	}

	// NewKeyFromSeed calculates a private key from a seed. It will panic if
	// len(seed) is not SeedSize. This function is provided for interoperability
	// with RFC 8032. RFC 8032's private keys correspond to seeds in this
	// package.
	func NewKeyFromSeed(seed []byte) PrivateKey {
	// Outline the function body so that the returned key can be stack-allocated.
	privateKey := make([]byte, PrivateKeySize)
	newKeyFromSeed(privateKey, seed)
	return privateKey
	}

	func newKeyFromSeed(privateKey, seed []byte) {
	if l := len(seed); l != SeedSize {
	panic("ed25519: bad seed length: " + strconv.Itoa(l))
	}

	digest := sha512.Sum512(seed)
	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, seed)
	copy(privateKey[32:], publicKeyBytes[:])
	}

	// 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 {
	// Outline the function body so that the returned signature can be
	// stack-allocated.
	signature := make([]byte, SignatureSize)
	sign(signature, privateKey, message)
	return signature
	}

	func signGeneric(signature, privateKey, message []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)

	copy(signature[:], encodedR[:])
	copy(signature[32:], s[:])
	}

	// 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 {
	return verify(publicKey, message, sig)
	}

	func verifyGeneric(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 s [32]byte
	copy(s[:], sig[32:])

	// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
	// the range [0, order) in order to prevent signature malleability.
	if !edwards25519.ScMinimal(&s) {
	return false
	}

	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &s)

	var checkR [32]byte
	R.ToBytes(&checkR)
	return bytes.Equal(sig[:32], checkR[:])
	}