Example #1
0
// Verify returns true iff sig is a valid signature of message by publicKey.
func Verify(publicKey *[PublicKeySize]byte, message []byte, sig *[SignatureSize]byte) bool {
	if sig[63]&224 != 0 {
		return false
	}

	var A edwards25519.ExtendedGroupElement
	if !A.FromBytes(publicKey) {
		return false
	}

	h := sha512.New()
	h.Write(sig[:32])
	h.Write(publicKey[:])
	h.Write(message)
	var digest [64]byte
	h.Sum(digest[:0])

	var hReduced [32]byte
	edwards25519.ScReduce(&hReduced, &digest)

	var R edwards25519.ProjectiveGroupElement
	var b [32]byte
	copy(b[:], sig[32:])
	edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &b)

	var checkR [32]byte
	R.ToBytes(&checkR)
	return subtle.ConstantTimeCompare(sig[:32], checkR[:]) == 1
}
Example #2
0
// PublicKeyToCurve25519 converts an Ed25519 public key into the curve25519
// public key that would be generated from the same private key.
func PublicKeyToCurve25519(curve25519Public *[32]byte, publicKey *[32]byte) bool {
	var A edwards25519.ExtendedGroupElement
	if !A.FromBytes(publicKey) {
		return false
	}

	// A.Z = 1 as a postcondition of FromBytes.
	var x edwards25519.FieldElement
	edwardsToMontgomeryX(&x, &A.Y)
	edwards25519.FeToBytes(curve25519Public, &x)
	return true
}