eddsa

Documentation

Overview

Package eddsa provides EdDSA signature scheme on bw6-756's twisted edwards curve.

See also

https://en.wikipedia.org/wiki/EdDSA

Example

// instantiate hash function
hFunc := hash.MIMC_BW6_756.New()

// create a eddsa key pair
privateKey, _ := GenerateKey(crand.Reader)
publicKey := privateKey.PublicKey

// generate a message (the size must be a multiple of the size of Fr)
var _msg fr.Element
_msg.SetRandom()
msg := _msg.Marshal()

// sign the message
signature, _ := privateKey.Sign(msg, hFunc)

// verifies signature
isValid, _ := publicKey.Verify(signature, msg, hFunc)
if !isValid {
	fmt.Println("1. invalid signature")
} else {
	fmt.Println("1. valid signature")
}

Output:

1. valid signature

Index

• type PrivateKey
  • func GenerateKey(r io.Reader) (*PrivateKey, error)
  • func (privKey *PrivateKey) Bytes() []byte
  • func (privKey *PrivateKey) Public() signature.PublicKey
  • func (privKey *PrivateKey) SetBytes(buf []byte) (int, error)
  • func (privKey *PrivateKey) Sign(message []byte, hFunc hash.Hash) ([]byte, error)
• type PublicKey
  • func (pk *PublicKey) Bytes() []byte
  • func (pub *PublicKey) Equal(x signature.PublicKey) bool
  • func (pk *PublicKey) SetBytes(buf []byte) (int, error)
  • func (pub *PublicKey) Verify(sigBin, message []byte, hFunc hash.Hash) (bool, error)
• type Signature
  • func (sig *Signature) Bytes() []byte
  • func (sig *Signature) SetBytes(buf []byte) (int, error)

Examples

• Package

Types

type PrivateKey

type PrivateKey struct {
	PublicKey PublicKey // copy of the associated public key
	// contains filtered or unexported fields
}

PrivateKey private key of an eddsa instance

func GenerateKey

func GenerateKey(r io.Reader) (*PrivateKey, error)

GenerateKey generates a public and private key pair.

func (*PrivateKey) Bytes

func (privKey *PrivateKey) Bytes() []byte

Bytes returns the binary representation of pk, as byte array publicKey||scalar||randSrc where publicKey is as publicKey.Bytes(), and scalar is in big endian, of size sizeFr.

func (*PrivateKey) Public

func (privKey *PrivateKey) Public() signature.PublicKey

Public returns the public key associated to the private key.

func (*PrivateKey) SetBytes

func (privKey *PrivateKey) SetBytes(buf []byte) (int, error)

SetBytes sets pk from buf, where buf is interpreted as publicKey||scalar||randSrc where publicKey is as publicKey.Bytes(), and scalar is in big endian, of size sizeFr. It returns the number byte read.

func (*PrivateKey) Sign

func (privKey *PrivateKey) Sign(message []byte, hFunc hash.Hash) ([]byte, error)

Sign sign a sequence of field elements For arbitrary strings use fr.Hash first Pure Eddsa version (see https://tools.ietf.org/html/rfc8032#page-8)

type PublicKey

type PublicKey struct {
	A twistededwards.PointAffine
}

PublicKey eddsa signature object cf https://en.wikipedia.org/wiki/EdDSA for notation

func (*PublicKey) Bytes

func (pk *PublicKey) Bytes() []byte

Bytes returns the binary representation of the public key follows https://tools.ietf.org/html/rfc8032#section-3.1 and returns a compressed representation of the point (x,y)

x, y are the coordinates of the point on the twisted Edwards as big endian integers. compressed representation store x with a parity bit to recompute y

func (*PublicKey) Equal

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

Equal compares 2 public keys

func (*PublicKey) SetBytes

func (pk *PublicKey) SetBytes(buf []byte) (int, error)

SetBytes sets p from binary representation in buf. buf represents a public key as x||y where x, y are interpreted as big endian binary numbers corresponding to the coordinates of a point on the twisted Edwards. It returns the number of bytes read from the buffer.

func (*PublicKey) Verify

func (pub *PublicKey) Verify(sigBin, message []byte, hFunc hash.Hash) (bool, error)

Verify verifies an eddsa signature

type Signature

type Signature struct {
	R twistededwards.PointAffine
	S [sizeFr]byte
}

Signature represents an eddsa signature cf https://en.wikipedia.org/wiki/EdDSA for notation

func (*Signature) Bytes

func (sig *Signature) Bytes() []byte

Bytes returns the binary representation of sig as a byte array of size 3*sizeFr x||y||s where

• x, y are the coordinates of a point on the twisted Edwards represented in big endian
• s=r+h(r,a,m) mod l, the Hasse bound guarantees that s is smaller than sizeFr (in particular it is supposed s is NOT blinded)

func (*Signature) SetBytes

func (sig *Signature) SetBytes(buf []byte) (int, error)

SetBytes sets sig from a buffer in binary. buf is read interpreted as x||y||s where

• x,y are the coordinates of a point on the twisted Edwards represented in big endian
• s=r+h(r,a,m) mod l, the Hasse bound guarantees that s is smaller than sizeFr (in particular it is supposed s is NOT blinded)

It returns the number of bytes read from buf.