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crypto / ecdsa

Package ecdsa

go1.15.3
Latest Go to latest

The highest tagged major version is .

Published: Oct 14, 2020 | License: BSD-3-Clause | Standard library

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

Code:

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

Examples

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 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. 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.

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.

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) 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 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.

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.

Package Files

Documentation was rendered with GOOS=linux and GOARCH=amd64.

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