secp256k1

README

secp256k1

This package is copied from https://github.com/ethereum/go-ethereum/tree/8fddf27a989e246659fd018ea9be37b2b4f55326/crypto/secp256k1

Unlike the rest of go-ethereum it is 3-clause BSD licensed so compatible with our Apache2.0 license. We opt to copy in here rather than depend on go-ethereum to avoid issues with vendoring of the GPL parts of that repository by downstream.

Duplicate Symbols

If a project is importing go-ethereum and the Cosmos SDK, cgo secp256k1 will only work on linux operating systems due to duplicated symbols. If you are testing on a mac, we recommend using a docker container or something similar.

To avoid duplicate symbol errors ldflags must be set to allow for multiple definitions.

Gcc

• go build -tags libsecp256k1_sdk -ldflags=all="-extldflags=-Wl,--allow-multiple-definition"

Clang

• go build -tags libsecp256k1_sdk -ldflags=all="-extldflags=-zmuldefs"

Documentation

Overview

Copyright 2010 The Go Authors. All rights reserved. Copyright 2011 ThePiachu. All rights reserved. Copyright 2015 Jeffrey Wilcke, Felix Lange, Gustav Simonsson. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
• Neither the name of Google Inc. nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
• The name of ThePiachu may not be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. nolint // this nolint lets us use this file in its original and unmodified form.

nolint // this nolint lets us use this file in its original and unmodified form.

Package secp256k1 wraps the bitcoin secp256k1 C library.

Index

• Variables
• func CompressPubkey(x, y *big.Int) []byte
• func DecompressPubkey(pubkey []byte) (x, y *big.Int)
• func RecoverPubkey(msg, sig []byte) ([]byte, error)
• func Sign(msg, seckey []byte) ([]byte, error)
• func VerifySignature(pubkey, msg, signature []byte) bool
• type BitCurve
  • func S256() *BitCurve
  • func (bitCurve *BitCurve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int)
  • func (BitCurve *BitCurve) Double(x1, y1 *big.Int) (*big.Int, *big.Int)
  • func (bitCurve *BitCurve) IsOnCurve(x, y *big.Int) bool
  • func (bitCurve *BitCurve) Marshal(x, y *big.Int) []byte
  • func (bitCurve *BitCurve) Params() *elliptic.CurveParams
  • func (BitCurve *BitCurve) ScalarBaseMult(k []byte) (*big.Int, *big.Int)
  • func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, *big.Int)
  • func (bitCurve *BitCurve) Unmarshal(data []byte) (x, y *big.Int)

Variables

var (
	ErrInvalidMsgLen       = errors.New("invalid message length, need 32 bytes")
	ErrInvalidSignatureLen = errors.New("invalid signature length")
	ErrInvalidRecoveryID   = errors.New("invalid signature recovery id")
	ErrInvalidKey          = errors.New("invalid private key")
	ErrInvalidPubkey       = errors.New("invalid public key")
	ErrSignFailed          = errors.New("signing failed")
	ErrRecoverFailed       = errors.New("recovery failed")
)

Functions

func CompressPubkey

func CompressPubkey(x, y *big.Int) []byte

CompressPubkey encodes a public key to 33-byte compressed format.

func DecompressPubkey

func DecompressPubkey(pubkey []byte) (x, y *big.Int)

DecompressPubkey parses a public key in the 33-byte compressed format. It returns non-nil coordinates if the public key is valid.

func RecoverPubkey

func RecoverPubkey(msg, sig []byte) ([]byte, error)

RecoverPubkey returns the public key of the signer. msg must be the 32-byte hash of the message to be signed. sig must be a 65-byte compact ECDSA signature containing the recovery id as the last element.

func Sign

func Sign(msg, seckey []byte) ([]byte, error)

Sign creates a recoverable ECDSA signature. The produced signature is in the 65-byte [R || S || V] format where V is 0 or 1.

The caller is responsible for ensuring that msg cannot be chosen directly by an attacker. It is usually preferable to use a cryptographic hash function on any input before handing it to this function.

func VerifySignature

func VerifySignature(pubkey, msg, signature []byte) bool

VerifySignature checks that the given pubkey created signature over message. The signature should be in [R || S] format.

Types

type BitCurve

type BitCurve struct {
	P       *big.Int // the order of the underlying field
	N       *big.Int // the order of the base point
	B       *big.Int // the constant of the BitCurve equation
	Gx, Gy  *big.Int // (x,y) of the base point
	BitSize int      // the size of the underlying field
}

A BitCurve represents a Koblitz Curve with a=0. See http://www.hyperelliptic.org/EFD/g1p/auto-shortw.html

func S256

func S256() *BitCurve

S256 returns a BitCurve which implements secp256k1.

func (*BitCurve) Add

func (bitCurve *BitCurve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int)

Add returns the sum of (x1,y1) and (x2,y2)

func (*BitCurve) Double

func (BitCurve *BitCurve) Double(x1, y1 *big.Int) (*big.Int, *big.Int)

Double returns 2*(x,y)

func (*BitCurve) IsOnCurve

func (bitCurve *BitCurve) IsOnCurve(x, y *big.Int) bool

IsOnCurve returns true if the given (x,y) lies on the BitCurve.

func (*BitCurve) Marshal

func (bitCurve *BitCurve) Marshal(x, y *big.Int) []byte

Marshal converts a point into the form specified in section 4.3.6 of ANSI X9.62.

func (*BitCurve) Params

func (bitCurve *BitCurve) Params() *elliptic.CurveParams

func (*BitCurve) ScalarBaseMult

func (BitCurve *BitCurve) ScalarBaseMult(k []byte) (*big.Int, *big.Int)

ScalarBaseMult returns k*G, where G is the base point of the group and k is an integer in big-endian form.

func (*BitCurve) ScalarMult

func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, *big.Int)

func (*BitCurve) Unmarshal

func (bitCurve *BitCurve) Unmarshal(data []byte) (x, y *big.Int)

Unmarshal converts a point, serialised by Marshal, into an x, y pair. On error, x = nil.