github.com/puppeth/go-ethereum@v0.8.6-0.20171014130046-e9295163aa25/crypto/signature_nocgo.go (about) 1 // Copyright 2017 The go-ethereum Authors 2 // This file is part of the go-ethereum library. 3 // 4 // The go-ethereum library is free software: you can redistribute it and/or modify 5 // it under the terms of the GNU Lesser General Public License as published by 6 // the Free Software Foundation, either version 3 of the License, or 7 // (at your option) any later version. 8 // 9 // The go-ethereum library is distributed in the hope that it will be useful, 10 // but WITHOUT ANY WARRANTY; without even the implied warranty of 11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 // GNU Lesser General Public License for more details. 13 // 14 // You should have received a copy of the GNU Lesser General Public License 15 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. 16 17 // +build nacl js nocgo 18 19 package crypto 20 21 import ( 22 "crypto/ecdsa" 23 "crypto/elliptic" 24 "fmt" 25 26 "github.com/btcsuite/btcd/btcec" 27 ) 28 29 func Ecrecover(hash, sig []byte) ([]byte, error) { 30 pub, err := SigToPub(hash, sig) 31 if err != nil { 32 return nil, err 33 } 34 bytes := (*btcec.PublicKey)(pub).SerializeUncompressed() 35 return bytes, err 36 } 37 38 func SigToPub(hash, sig []byte) (*ecdsa.PublicKey, error) { 39 // Convert to btcec input format with 'recovery id' v at the beginning. 40 btcsig := make([]byte, 65) 41 btcsig[0] = sig[64] + 27 42 copy(btcsig[1:], sig) 43 44 pub, _, err := btcec.RecoverCompact(btcec.S256(), btcsig, hash) 45 return (*ecdsa.PublicKey)(pub), err 46 } 47 48 // Sign calculates an ECDSA signature. 49 // 50 // This function is susceptible to chosen plaintext attacks that can leak 51 // information about the private key that is used for signing. Callers must 52 // be aware that the given hash cannot be chosen by an adversery. Common 53 // solution is to hash any input before calculating the signature. 54 // 55 // The produced signature is in the [R || S || V] format where V is 0 or 1. 56 func Sign(hash []byte, prv *ecdsa.PrivateKey) ([]byte, error) { 57 if len(hash) != 32 { 58 return nil, fmt.Errorf("hash is required to be exactly 32 bytes (%d)", len(hash)) 59 } 60 if prv.Curve != btcec.S256() { 61 return nil, fmt.Errorf("private key curve is not secp256k1") 62 } 63 sig, err := btcec.SignCompact(btcec.S256(), (*btcec.PrivateKey)(prv), hash, false) 64 if err != nil { 65 return nil, err 66 } 67 // Convert to Ethereum signature format with 'recovery id' v at the end. 68 v := sig[0] - 27 69 copy(sig, sig[1:]) 70 sig[64] = v 71 return sig, nil 72 } 73 74 // S256 returns an instance of the secp256k1 curve. 75 func S256() elliptic.Curve { 76 return btcec.S256() 77 }