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			8.2 KiB
		
	
	
	
		
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			321 lines
		
	
	
		
			8.2 KiB
		
	
	
	
		
			Go
		
	
	
	
	
	
//
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// Copyright Coinbase, Inc. All Rights Reserved.
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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// This file implements the Ed25519 signature algorithm. See
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// https://ed25519.cr.yp.to/.
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//
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// These functions are also compatible with the “Ed25519” function defined in
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// RFC 8032. However, unlike RFC 8032's formulation, this package's private key
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// representation includes a public key suffix to make multiple signing
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// operations with the same key more efficient. This package refers to the RFC
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// 8032 private key as the “seed”.
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// This code is a port of the public domain, “ref10” implementation of ed25519
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// from SUPERCOP.
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package nem
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import (
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	"bytes"
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	"crypto"
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	cryptorand "crypto/rand"
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	"fmt"
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	"io"
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	"strconv"
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	"filippo.io/edwards25519"
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	"golang.org/x/crypto/sha3"
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	"source.quilibrium.com/quilibrium/monorepo/nekryptology/internal"
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)
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const (
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	// PublicKeySize is the size, in bytes, of public keys as used in this package.
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	PublicKeySize = 32
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	// PrivateKeySize is the size, in bytes, of private keys as used in this package.
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	PrivateKeySize = 64
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	// SignatureSize is the size, in bytes, of signatures generated and verified by this package.
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	SignatureSize = 64
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	// SeedSize is the size, in bytes, of private key seeds. These are the private key representations used by RFC 8032.
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	SeedSize = 32
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)
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// PublicKey is the type of Ed25519 public keys.
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type PublicKey []byte
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// PrivateKey is the type of Ed25519 private keys. It implements crypto.Signer.
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type PrivateKey []byte
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// Bytes returns the publicKey in byte array
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func (p PublicKey) Bytes() []byte {
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	return p
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}
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// Public returns the PublicKey corresponding to priv.
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func (priv PrivateKey) Public() crypto.PublicKey {
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	publicKey := make([]byte, PublicKeySize)
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	copy(publicKey, priv[32:])
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	return PublicKey(publicKey)
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}
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func Keccak512(data []byte) ([]byte, error) {
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	k512 := sha3.NewLegacyKeccak512()
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	_, err := k512.Write(data)
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	if err != nil {
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		return nil, err
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	}
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	return k512.Sum(nil), nil
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}
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// Seed returns the private key seed corresponding to priv. It is provided for
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// interoperability with RFC 8032. RFC 8032's private keys correspond to seeds
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// in this package.
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func (priv PrivateKey) Seed() []byte {
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	seed := make([]byte, SeedSize)
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	copy(seed, priv[:32])
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	return seed
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}
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// Sign signs the given message with priv.
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// Ed25519 performs two passes over messages to be signed and therefore cannot
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// handle pre-hashed messages. Thus opts.HashFunc() must return zero to
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// indicate the message hasn't been hashed. This can be achieved by passing
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// crypto.Hash(0) as the value for opts.
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func (priv PrivateKey) Sign(rand io.Reader, message []byte, opts crypto.SignerOpts) (signature []byte, err error) {
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	if opts.HashFunc() != crypto.Hash(0) {
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		return nil, fmt.Errorf("ed25519: cannot sign hashed message")
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	}
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	sig, err := Sign(priv, message)
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	if err != nil {
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		return nil, err
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	}
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	return sig, nil
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}
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// GenerateKey generates a public/private key pair using entropy from rand.
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// If rand is nil, crypto/rand.Reader will be used.
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func GenerateKey(rand io.Reader) (PublicKey, PrivateKey, error) {
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	if rand == nil {
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		rand = cryptorand.Reader
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	}
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	seed := make([]byte, SeedSize)
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	if _, err := io.ReadFull(rand, seed); err != nil {
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		return nil, nil, err
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	}
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	privateKey, err := NewKeyFromSeed(seed)
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	if err != nil {
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		return nil, nil, err
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	}
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	publicKey := make([]byte, PublicKeySize)
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	copy(publicKey, privateKey[32:])
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	return publicKey, privateKey, nil
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}
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// NewKeyFromSeed calculates a private key from a seed. It will panic if
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// len(seed) is not SeedSize. This function is provided for interoperability
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// with RFC 8032. RFC 8032's private keys correspond to seeds in this
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// package.
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func NewKeyFromSeed(seed []byte) (PrivateKey, error) {
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	// Outline the function body so that the returned key can be stack-allocated.
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	privateKey := make([]byte, PrivateKeySize)
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	err := newKeyFromSeed(privateKey, seed)
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	if err != nil {
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		return nil, err
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	}
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	return privateKey, nil
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}
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func newKeyFromSeed(privateKey, seed []byte) error {
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	if l := len(seed); l != SeedSize {
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		return fmt.Errorf("ed25519: bad seed length: " + strconv.Itoa(l))
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	}
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	// Weird required step to get compatibility with the NEM test vectors
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	// Have to reverse the bytes from the given seed
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	digest, err := Keccak512(internal.ReverseScalarBytes(seed))
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	if err != nil {
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		return err
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	}
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	sc, err := edwards25519.NewScalar().SetBytesWithClamping(digest[:32])
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	if err != nil {
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		return err
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	}
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	A := edwards25519.Point{}
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	A.ScalarBaseMult(sc)
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	publicKeyBytes := A.Bytes()
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	copy(privateKey, seed)
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	copy(privateKey[32:], publicKeyBytes[:])
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	return nil
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}
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// Sign signs the message with privateKey and returns a signature. It will
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// panic if len(privateKey) is not PrivateKeySize.
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func Sign(privateKey PrivateKey, message []byte) ([]byte, error) {
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	// Outline the function body so that the returned signature can be
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	// stack-allocated.
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	signature := make([]byte, SignatureSize)
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	err := sign(signature, privateKey, message)
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	if err != nil {
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		return nil, err
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	}
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	return signature, nil
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}
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func sign(signature, privateKey, message []byte) error {
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	if l := len(privateKey); l != PrivateKeySize {
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		return fmt.Errorf("ed25519: bad private key length: " + strconv.Itoa(l))
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	}
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	seed := privateKey[:32]
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	digest, err := Keccak512(internal.ReverseScalarBytes(seed))
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	if err != nil {
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		return err
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	}
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	// H(seed) ie. privkey
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	expandedSecretKey := digest[:32]
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	sc, err := edwards25519.NewScalar().SetBytesWithClamping(expandedSecretKey)
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	if err != nil {
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		return err
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	}
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	// r = H(H(seed) + msg)
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	hEngine := sha3.NewLegacyKeccak512()
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	_, err = hEngine.Write(digest[32:])
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	if err != nil {
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		return err
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	}
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	_, err = hEngine.Write(message)
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	if err != nil {
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		return err
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	}
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	var hOut1 [64]byte
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	hEngine.Sum(hOut1[:0])
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	// hash output -> scalar
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	// Take 64 byte output from keccak512 so need to set bytes as long
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	r, err := edwards25519.NewScalar().SetUniformBytes(hOut1[:])
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	if err != nil {
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		return err
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	}
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	// R = r*G
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	R := edwards25519.Point{}
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	R.ScalarBaseMult(r)
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	RBytes := R.Bytes()
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	// s = H(R + pubkey + msg)
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	hEngine.Reset()
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	_, err = hEngine.Write(RBytes)
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	if err != nil {
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		return err
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	}
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	_, err = hEngine.Write(privateKey[32:])
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	if err != nil {
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		return err
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	}
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	_, err = hEngine.Write(message)
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	if err != nil {
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		return err
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	}
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	var hOut2 [64]byte
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	hEngine.Sum(hOut2[:0])
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	// hash output -> scalar
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	// Take 64 byte output from keccak512 so need to set bytes as long
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	h, err := edwards25519.NewScalar().SetUniformBytes(hOut2[:])
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	if err != nil {
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		return err
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	}
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	// s = (r + h * privKey)
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	s := edwards25519.NewScalar().MultiplyAdd(h, sc, r)
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	copy(signature[:], RBytes)
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	copy(signature[32:], s.Bytes())
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	return nil
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}
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// Verify reports whether sig is a valid signature of message by publicKey. It
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// will panic if len(publicKey) is not PublicKeySize.
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// Previously publicKey is of type PublicKey
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func Verify(publicKey PublicKey, message, sig []byte) (bool, error) {
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	if l := len(publicKey); l != PublicKeySize {
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		return false, fmt.Errorf("ed25519: bad public key length: " + strconv.Itoa(l))
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	}
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	if len(sig) != SignatureSize || sig[63]&224 != 0 {
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		return false, fmt.Errorf("ed25519: bad signature size: " + strconv.Itoa(len(sig)))
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	}
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	RBytes := sig[:32]
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	sBytes := sig[32:]
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	var publicKeyBytes [32]byte
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	copy(publicKeyBytes[:], publicKey)
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	A := edwards25519.Point{}
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	_, err := A.SetBytes(publicKeyBytes[:])
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	if err != nil {
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		return false, err
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	}
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	negA := edwards25519.Point{}
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	negA.Negate(&A)
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	// h = H(R + pubkey + msg)
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	hEngine := sha3.NewLegacyKeccak512()
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	_, err = hEngine.Write(RBytes)
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	if err != nil {
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		return false, err
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	}
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	_, err = hEngine.Write(publicKeyBytes[:])
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	if err != nil {
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		return false, err
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	}
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	_, err = hEngine.Write(message)
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	if err != nil {
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		return false, err
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	}
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	var hOut1 [64]byte
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	hEngine.Sum(hOut1[:0])
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	// hash output -> scalar
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	// Take 64 byte output from keccak512 so need to set bytes as long
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	h, err := edwards25519.NewScalar().SetUniformBytes(hOut1[:])
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	if err != nil {
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		return false, err
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	}
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	// s was generated in sign so can set as canonical
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	s, err := edwards25519.NewScalar().SetCanonicalBytes(sBytes)
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	if err != nil {
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		return false, err
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	}
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	// R' = s*G - h*Pubkey = h*negPubkey + s*G
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	RPrime := edwards25519.Point{}
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	RPrime.VarTimeDoubleScalarBaseMult(h, &negA, s)
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	RPrimeBytes := RPrime.Bytes()
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	// Check R == R'
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	return bytes.Equal(RBytes, RPrimeBytes), nil
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}
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