// Sign signs the message with privateKey and returns a signature.
func Sign(privateKey *[32]byte, message []byte, random [64]byte) *[64]byte {
// Calculate Ed25519 public key from Curve25519 private key
var A edwards25519.ExtendedGroupElement
var publicKey [32]byte
edwards25519.GeScalarMultBase(&A, privateKey)
A.ToBytes(&publicKey)
// Calculate r
diversifier := [32]byte{
0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}
var r [64]byte
h := sha512.New()
h.Write(diversifier[:])
h.Write(privateKey[:])
h.Write(message)
h.Write(random[:])
h.Sum(r[:0])
// Calculate R
var rReduced [32]byte
edwards25519.ScReduce(&rReduced, &r)
var R edwards25519.ExtendedGroupElement
edwards25519.GeScalarMultBase(&R, &rReduced)
var encodedR [32]byte
R.ToBytes(&encodedR)
// Calculate S = r + SHA2-512(R || A_ed || msg) * a (mod L)
var hramDigest [64]byte
h.Reset()
h.Write(encodedR[:])
h.Write(publicKey[:])
h.Write(message)
h.Sum(hramDigest[:0])
var hramDigestReduced [32]byte
edwards25519.ScReduce(&hramDigestReduced, &hramDigest)
var s [32]byte
edwards25519.ScMulAdd(&s, &hramDigestReduced, privateKey, &rReduced)
signature := new([64]byte)
copy(signature[:], encodedR[:])
copy(signature[32:], s[:])
signature[63] |= publicKey[31] & 0x80
return signature
}
// Sign signs the message with privateKey and returns a signature.
func Sign(privateKey *[PrivateKeySize]byte, message []byte) *[SignatureSize]byte {
h := sha512.New()
h.Write(privateKey[:32])
var digest1, messageDigest, hramDigest [64]byte
var expandedSecretKey [32]byte
h.Sum(digest1[:0])
copy(expandedSecretKey[:], digest1[:])
expandedSecretKey[0] &= 248
expandedSecretKey[31] &= 63
expandedSecretKey[31] |= 64
h.Reset()
h.Write(digest1[32:])
h.Write(message)
h.Sum(messageDigest[:0])
var messageDigestReduced [32]byte
edwards25519.ScReduce(&messageDigestReduced, &messageDigest)
var R edwards25519.ExtendedGroupElement
edwards25519.GeScalarMultBase(&R, &messageDigestReduced)
var encodedR [32]byte
R.ToBytes(&encodedR)
h.Reset()
h.Write(encodedR[:])
h.Write(privateKey[32:])
h.Write(message)
h.Sum(hramDigest[:0])
var hramDigestReduced [32]byte
edwards25519.ScReduce(&hramDigestReduced, &hramDigest)
var s [32]byte
edwards25519.ScMulAdd(&s, &hramDigestReduced, &expandedSecretKey, &messageDigestReduced)
signature := new([64]byte)
copy(signature[:], encodedR[:])
copy(signature[32:], s[:])
return signature
}
