btcutil

README

btcutil

Utility functions for Bitcoin elliptic curve cryptography.

Install with

go get github.com/mndrix/btcutil

Documentation

Index

• func Add(a, b *ecdsa.PublicKey) *ecdsa.PublicKey
• func BlindMessage(rState *BlindRequesterState, Q, R *ecdsa.PublicKey, m *big.Int) *big.Int
• func BlindSession(sState *BlindSignerState) (*ecdsa.PublicKey, *ecdsa.PublicKey)
• func BlindSign(sState *BlindSignerState, R *ecdsa.PublicKey, mHat *big.Int) *big.Int
• func BlindVerify(Q *ecdsa.PublicKey, sig *BlindSignature) bool
• func ECDH(priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey) *big.Int
• func GenerateKey(rand io.Reader) (*ecdsa.PrivateKey, error)
• func KeysEqual(a, b *ecdsa.PublicKey) bool
• func RandFieldElement(rand io.Reader) (k *big.Int, err error)
• func ScalarBaseMult(k *big.Int) *ecdsa.PublicKey
• func ScalarMult(k *big.Int, B *ecdsa.PublicKey) *ecdsa.PublicKey
• func Secp256k1() elliptic.Curve
• type BlindRequesterState
• type BlindSignature
  • func BlindExtract(rState *BlindRequesterState, sHat *big.Int) *BlindSignature
• type BlindSignerState
• type KoblitzCurve
  • func (curve *KoblitzCurve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int)
  • func (curve *KoblitzCurve) Double(x1, y1 *big.Int) (*big.Int, *big.Int)
  • func (curve *KoblitzCurve) IsOnCurve(x, y *big.Int) bool
  • func (curve *KoblitzCurve) Params() *elliptic.CurveParams
  • func (curve *KoblitzCurve) ScalarBaseMult(k []byte) (*big.Int, *big.Int)
  • func (curve *KoblitzCurve) ScalarMult(Bx, By *big.Int, k []byte) (*big.Int, *big.Int)

Functions

func Add

func Add(a, b *ecdsa.PublicKey) *ecdsa.PublicKey

Adds two points to create a third. Points are represented as ECDSA public keys.

func BlindMessage

func BlindMessage(rState *BlindRequesterState, Q, R *ecdsa.PublicKey, m *big.Int) *big.Int

Calculates a blinded version of message m

func BlindSession

func BlindSession(sState *BlindSignerState) (*ecdsa.PublicKey, *ecdsa.PublicKey)

Request that the signer start a blind signature protocol. Returns the signer's public key and an EC point named R.

func BlindSign

func BlindSign(sState *BlindSignerState, R *ecdsa.PublicKey, mHat *big.Int) *big.Int

Signs a blinded message

func BlindVerify

func BlindVerify(Q *ecdsa.PublicKey, sig *BlindSignature) bool

func ECDH

func ECDH(priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey) *big.Int

Calculate a shared secret using elliptic curve Diffie-Hellman

func GenerateKey

func GenerateKey(rand io.Reader) (*ecdsa.PrivateKey, error)

GenerateKey generates a public and private key pair

func KeysEqual

func KeysEqual(a, b *ecdsa.PublicKey) bool

func RandFieldElement

func RandFieldElement(rand io.Reader) (k *big.Int, err error)

RandFieldElement returns a random element of the field underlying the given curve using the procedure given in [NSA] A.2.1.

Implementation copied from Go's crypto/ecdsa package since the function wasn't public. Modified to always use secp256k1 curve.

func ScalarBaseMult

func ScalarBaseMult(k *big.Int) *ecdsa.PublicKey

Multiplies the base G by a large integer. The resulting point is represented as an ECDSA public key since that's typically how they're used.

func ScalarMult

func ScalarMult(k *big.Int, B *ecdsa.PublicKey) *ecdsa.PublicKey

Multiply a large integer and a point. The resulting point is represented as an ECDSA public key.

func Secp256k1

func Secp256k1() elliptic.Curve

Types

type BlindRequesterState

type BlindRequesterState struct {

	// shareable stuff
	F    *ecdsa.PublicKey
	X0   *big.Int //
	Mhat *big.Int // called m̂ in the paper
	// contains filtered or unexported fields
}

type BlindSignature

type BlindSignature struct {
	M, S *big.Int // called m and s in the paper
	F    *ecdsa.PublicKey
}

func BlindExtract

func BlindExtract(rState *BlindRequesterState, sHat *big.Int) *BlindSignature

Extract true signature from the blind signature

type BlindSignerState

type BlindSignerState struct {

	// shareable stuff
	Q *ecdsa.PublicKey
	// contains filtered or unexported fields
}

type KoblitzCurve

type KoblitzCurve 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 KoblitzCurve equation
	Gx, Gy  *big.Int // (x,y) of the base point
	BitSize int      // the size of the underlying field
}

A Koblitz Curve with a=0.

func (*KoblitzCurve) Add

func (curve *KoblitzCurve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int)

func (*KoblitzCurve) Double

func (curve *KoblitzCurve) Double(x1, y1 *big.Int) (*big.Int, *big.Int)

func (*KoblitzCurve) IsOnCurve

func (curve *KoblitzCurve) IsOnCurve(x, y *big.Int) bool

func (*KoblitzCurve) Params

func (curve *KoblitzCurve) Params() *elliptic.CurveParams

func (*KoblitzCurve) ScalarBaseMult

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

func (*KoblitzCurve) ScalarMult

func (curve *KoblitzCurve) ScalarMult(Bx, By *big.Int, k []byte) (*big.Int, *big.Int)