Function Sign

sign/schnorr/schnorr.go:32–58

Sign creates a Sign signature from a msg and a private key. This signature can be verified with VerifySchnorr. It's also a valid EdDSA signature when using the edwards25519 Group.

(s Suite, private kyber.Scalar, msg []byte)

// signature can be verified with VerifySchnorr. It's also a valid EdDSA
// signature when using the edwards25519 Group.
func Sign(s Suite, private kyber.Scalar, msg []byte) ([]byte, error) {
	var g kyber.Group = s
	// create random secret k and public point commitment R
	k := g.Scalar().Pick(s.RandomStream())
	R := g.Point().Mul(k, nil)

	// create hash(public || R || message)
	public := g.Point().Mul(private, nil)
	h, err := hash(g, public, R, msg)
	if err != nil {
		return nil, err
	}

	// compute response s = k + x*h
	xh := g.Scalar().Mul(private, h)
	S := g.Scalar().Add(k, xh)

	// return R || s
	var b bytes.Buffer
	if _, err := R.MarshalTo(&b); err != nil {
		return nil, err
	}
	if _, err := S.MarshalTo(&b); err != nil {
		return nil, err
	}
	return b.Bytes(), nil
}

// Verify verifies a given Schnorr signature. It returns nil iff the
// given signature is valid.