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  }