github.com/Elemental-core/elementalcore@v0.0.0-20191206075037-63891242267a/crypto/signature_cgo.go (about)

     1  // Copyright 2017 The elementalcore Authors
     2  // This file is part of the elementalcore library.
     3  //
     4  // The elementalcore 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 elementalcore 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 elementalcore 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/Elemental-core/elementalcore/common/math"
    27  	"github.com/Elemental-core/elementalcore/crypto/secp256k1"
    28  )
    29  
    30  func Ecrecover(hash, sig []byte) ([]byte, error) {
    31  	return secp256k1.RecoverPubkey(hash, sig)
    32  }
    33  
    34  func SigToPub(hash, sig []byte) (*ecdsa.PublicKey, error) {
    35  	s, err := Ecrecover(hash, sig)
    36  	if err != nil {
    37  		return nil, err
    38  	}
    39  
    40  	x, y := elliptic.Unmarshal(S256(), s)
    41  	return &ecdsa.PublicKey{Curve: S256(), X: x, Y: y}, nil
    42  }
    43  
    44  // Sign calculates an ECDSA signature.
    45  //
    46  // This function is susceptible to chosen plaintext attacks that can leak
    47  // information about the private key that is used for signing. Callers must
    48  // be aware that the given hash cannot be chosen by an adversery. Common
    49  // solution is to hash any input before calculating the signature.
    50  //
    51  // The produced signature is in the [R || S || V] format where V is 0 or 1.
    52  func Sign(hash []byte, prv *ecdsa.PrivateKey) (sig []byte, err error) {
    53  	if len(hash) != 32 {
    54  		return nil, fmt.Errorf("hash is required to be exactly 32 bytes (%d)", len(hash))
    55  	}
    56  	seckey := math.PaddedBigBytes(prv.D, prv.Params().BitSize/8)
    57  	defer zeroBytes(seckey)
    58  	return secp256k1.Sign(hash, seckey)
    59  }
    60  
    61  // S256 returns an instance of the secp256k1 curve.
    62  func S256() elliptic.Curve {
    63  	return secp256k1.S256()
    64  }