ecdh

README

change log

2018-06-21

• add x509 marshal and unmarshal
• support -param_enc explicit
• fixed crypto/elliptic: unexpected P256.ScalarMult result, issue: https://github.com/golang/go/issues/26020

ECDH

This is a go implementation of elliptical curve diffie-hellman key exchange method. It supports the NIST curves (and any curves using the elliptic.Curve go interface) as well as djb's curve25519.

The library handles generating of keys, generating a shared secret, and the (un)marshalling of the elliptical curve keys into slices of bytes.

Warning and Disclaimer

I am not a cryptographer, this was written as part of a personal project to learn about cryptographic systems and protocols. No claims as to the security of this library are made, I would not advise using it for anything that requires any level of security. Pull requests or issues about security flaws are however still welcome.

Compatibility

Works with go 1.2 onwards.

TODO

• Improve documentation

Documentation

Index

• type ECDH
• type EllipticECDH
  • func NewEllipticECDH(curve elliptic.Curve) *EllipticECDH
  • func (e *EllipticECDH) GenerateKey(rand io.Reader) (*EllipticPrivateKey, *EllipticPublicKey, error)
  • func (e *EllipticECDH) GenerateSharedSecret(priv *EllipticPrivateKey, pub *EllipticPublicKey) ([]byte, error)
  • func (e *EllipticECDH) Marshal(pub *EllipticPublicKey) ([]byte, error)
  • func (e *EllipticECDH) Unmarshal(data []byte) (*EllipticPublicKey, error)
  • func (e *EllipticECDH) X509MarshalPrivateKey(priKey *EllipticPrivateKey) ([]byte, error)
  • func (e *EllipticECDH) X509MarshalPublicKey(pub *EllipticPublicKey) ([]byte, error)
  • func (e *EllipticECDH) X509UnmarshalPrivateKey(pemBytes []byte) (*EllipticPrivateKey, error)
  • func (e *EllipticECDH) X509UnmarshalPublicKey(data []byte) (*EllipticPublicKey, error)
• type EllipticPrivateKey
• type EllipticPublicKey

Types

type ECDH

type ECDH interface {
	GenerateKey(io.Reader) (*EllipticPrivateKey, *EllipticPublicKey, error)
	Marshal(priKey *EllipticPublicKey) ([]byte, error)
	Unmarshal([]byte) (*EllipticPublicKey, error)
	// X509MarshalPublicKey(p crypto.PublicKey) ([]byte, error)
	// X509UnmarshalPublicKey(data []byte) (crypto.PublicKey, error)
	GenerateSharedSecret(*EllipticPrivateKey, *EllipticPublicKey) ([]byte, error)
}

The main interface for ECDH key exchange.

type EllipticECDH

type EllipticECDH struct {
	ECDH
	// contains filtered or unexported fields
}

func NewEllipticECDH

func NewEllipticECDH(curve elliptic.Curve) *EllipticECDH

NewEllipticECDH creates a new instance of ECDH with the given elliptic.Curve curve to use as the elliptical curve for elliptical curve diffie-hellman.

func (*EllipticECDH) GenerateKey

func (e *EllipticECDH) GenerateKey(rand io.Reader) (*EllipticPrivateKey, *EllipticPublicKey, error)

func (*EllipticECDH) GenerateSharedSecret

func (e *EllipticECDH) GenerateSharedSecret(priv *EllipticPrivateKey, pub *EllipticPublicKey) ([]byte, error)

GenerateSharedSecret takes in a public key and a private key and generates a shared secret.

RFC5903 Section 9 states we should only return x.

func (*EllipticECDH) Marshal

func (e *EllipticECDH) Marshal(pub *EllipticPublicKey) ([]byte, error)

func (*EllipticECDH) Unmarshal

func (e *EllipticECDH) Unmarshal(data []byte) (*EllipticPublicKey, error)

func (*EllipticECDH) X509MarshalPrivateKey

func (e *EllipticECDH) X509MarshalPrivateKey(priKey *EllipticPrivateKey) ([]byte, error)

func (*EllipticECDH) X509MarshalPublicKey

func (e *EllipticECDH) X509MarshalPublicKey(pub *EllipticPublicKey) ([]byte, error)

func (*EllipticECDH) X509UnmarshalPrivateKey

func (e *EllipticECDH) X509UnmarshalPrivateKey(pemBytes []byte) (*EllipticPrivateKey, error)

func (*EllipticECDH) X509UnmarshalPublicKey

func (e *EllipticECDH) X509UnmarshalPublicKey(data []byte) (*EllipticPublicKey, error)

type EllipticPrivateKey

type EllipticPrivateKey struct {
	EllipticPublicKey
	D *big.Int
}

type EllipticPublicKey

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