ecdsa

Documentation

Overview

Package ecdsa implements the Elliptic Curve Digital Signature Algorithm, as defined in FIPS 186-3.

This implementation derives the nonce from an AES-CTR CSPRNG keyed by:

SHA2-512(priv.D || entropy || hash)[:32]

The CSPRNG key is indifferentiable from a random oracle as shown in [Coron], the AES-CTR stream is indifferentiable from a random oracle under standard cryptographic assumptions (see [Larsson] for examples).

References:

[Coron]
  https://cs.nyu.edu/~dodis/ps/merkle.pdf
[Larsson]
  https://www.nada.kth.se/kurser/kth/2D1441/semteo03/lecturenotes/assump.pdf

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))

	r, s, err := ecdsa.Sign(rand.Reader, privateKey, hash[:])
	if err != nil {
		panic(err)
	}
	fmt.Printf("signature: (0x%x, 0x%x)\n", r, s)

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

Index

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

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. The security of the private key depends on the entropy of rand.

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.

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) 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 should use the Sign function in this package directly.

type PublicKey

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

PublicKey represents an ECDSA public key.