ecdsa

Documentation

Overview

Package ecdsa implements the Elliptic Curve Digital Signature Algorithm, as defined in FIPS 186-4 and SEC 1, Version 2.0.

Signatures generated by this package are not deterministic, but entropy is mixed with the private key and the message, achieving the same level of security in case of randomness source failure.

Example

package main

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/sha256"
	"fmt"
)

func main() {
	privateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		panic(err)
	}

	msg := "hello, world"
	hash := sha256.Sum256([]byte(msg))

	sig, err := ecdsa.SignASN1(rand.Reader, privateKey, hash[:])
	if err != nil {
		panic(err)
	}
	fmt.Printf("signature: %x\n", sig)

	valid := ecdsa.VerifyASN1(&privateKey.PublicKey, hash[:], sig)
	fmt.Println("signature verified:", valid)
}

Index

• func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err error)
• func SignASN1(rand io.Reader, priv *PrivateKey, hash []byte) ([]byte, error)
• func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool
• func VerifyASN1(pub *PublicKey, hash, sig []byte) bool
• type PrivateKey
  • func GenerateKey(c elliptic.Curve, rand io.Reader) (*PrivateKey, error)
  • func (k *PrivateKey) ECDH() (*ecdh.PrivateKey, error)
  • func (priv *PrivateKey) Equal(x crypto.PrivateKey) bool
  • func (priv *PrivateKey) Public() crypto.PublicKey
  • func (priv *PrivateKey) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error)
• type PublicKey
  • func (k *PublicKey) ECDH() (*ecdh.PublicKey, error)
  • func (pub *PublicKey) Equal(x crypto.PublicKey) bool

Examples

• Package

Functions

func Sign

func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err error)

Sign signs a hash (which should be the result of hashing a larger message) using the private key, priv. If the hash is longer than the bit-length of the private key's curve order, the hash will be truncated to that length. It returns the signature as a pair of integers. Most applications should use SignASN1 instead of dealing directly with r, s.

func SignASN1

func SignASN1(rand io.Reader, priv *PrivateKey, hash []byte) ([]byte, error)

SignASN1 signs a hash (which should be the result of hashing a larger message) using the private key, priv. If the hash is longer than the bit-length of the private key's curve order, the hash will be truncated to that length. It returns the ASN.1 encoded signature.

func Verify

func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool

Verify verifies the signature in r, s of hash using the public key, pub. Its return value records whether the signature is valid. Most applications should use VerifyASN1 instead of dealing directly with r, s.

func VerifyASN1

func VerifyASN1(pub *PublicKey, hash, sig []byte) bool

VerifyASN1 verifies the ASN.1 encoded signature, sig, of hash using the public key, pub. Its return value records whether the signature is valid.

Types

type PrivateKey

type PrivateKey struct {
	PublicKey
	D *big.Int
}

PrivateKey represents an ECDSA private key.

func GenerateKey

func GenerateKey(c elliptic.Curve, rand io.Reader) (*PrivateKey, error)

GenerateKey generates a public and private key pair.

func (*PrivateKey) ECDH

func (k *PrivateKey) ECDH() (*ecdh.PrivateKey, error)

ECDH returns k as a ecdh.PrivateKey. It returns an error if the key is invalid according to the definition of ecdh.Curve.NewPrivateKey, or if the Curve is not supported by crypto/ecdh.

func (*PrivateKey) Equal

func (priv *PrivateKey) Equal(x crypto.PrivateKey) bool

Equal reports whether priv and x have the same value.

See PublicKey.Equal for details on how Curve is compared.

func (*PrivateKey) Public

func (priv *PrivateKey) Public() crypto.PublicKey

Public returns the public key corresponding to priv.

func (*PrivateKey) Sign

func (priv *PrivateKey) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error)

Sign signs digest with priv, reading randomness from rand. The opts argument is not currently used but, in keeping with the crypto.Signer interface, should be the hash function used to digest the message.

This method implements crypto.Signer, which is an interface to support keys where the private part is kept in, for example, a hardware module. Common uses can use the SignASN1 function in this package directly.

type PublicKey

type PublicKey struct {
	elliptic.Curve
	X, Y *big.Int
}

PublicKey represents an ECDSA public key.

func (*PublicKey) ECDH

func (k *PublicKey) ECDH() (*ecdh.PublicKey, error)

ECDH returns k as a ecdh.PublicKey. It returns an error if the key is invalid according to the definition of ecdh.Curve.NewPublicKey, or if the Curve is not supported by crypto/ecdh.

func (*PublicKey) Equal

func (pub *PublicKey) Equal(x crypto.PublicKey) bool

Equal reports whether pub and x have the same value.

Two keys are only considered to have the same value if they have the same Curve value. Note that for example elliptic.P256() and elliptic.P256().Params() are different values, as the latter is a generic not constant time implementation.