// GenerateKey generates a public/private key pair using entropy from rand.
// If rand is nil, crypto/rand.Reader will be used.
func GenerateKey(rand io.Reader) (publicKey PublicKey, privateKey PrivateKey, err error) {
if rand == nil {
rand = cryptorand.Reader
}
privateKey = make([]byte, PrivateKeySize)
publicKey = make([]byte, PublicKeySize)
_, err = io.ReadFull(rand, privateKey[:32])
if err != nil {
return nil, nil, err
}
digest := sha512.Sum512(privateKey[:32])
digest[0] &= 248
digest[31] &= 127
digest[31] |= 64
var A edwards25519.ExtendedGroupElement
var hBytes [32]byte
copy(hBytes[:], digest[:])
edwards25519.GeScalarMultBase(&A, &hBytes)
var publicKeyBytes [32]byte
A.ToBytes(&publicKeyBytes)
copy(privateKey[32:], publicKeyBytes[:])
copy(publicKey, publicKeyBytes[:])
return publicKey, privateKey, nil
}
// Sign signs the message with privateKey and returns a signature. It will
// panic if len(privateKey) is not PrivateKeySize.
func Sign(privateKey PrivateKey, message []byte) []byte {
if l := len(privateKey); l != PrivateKeySize {
panic("ed25519: bad private key length: " + strconv.Itoa(l))
}
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 := make([]byte, SignatureSize)
copy(signature[:], encodedR[:])
copy(signature[32:], s[:])
return signature
}
func TestUnmarshalMarshal(t *testing.T) {
pub, _, _ := GenerateKey(rand.Reader)
var A edwards25519.ExtendedGroupElement
var pubBytes [32]byte
copy(pubBytes[:], pub)
if !A.FromBytes(&pubBytes) {
t.Fatalf("ExtendedGroupElement.FromBytes failed")
}
var pub2 [32]byte
A.ToBytes(&pub2)
if pubBytes != pub2 {
t.Errorf("FromBytes(%v)->ToBytes does not round-trip, got %x\n", pubBytes, pub2)
}
}
// Verify reports whether sig is a valid signature of message by publicKey. It
// will panic if len(publicKey) is not PublicKeySize.
func Verify(publicKey PublicKey, message, sig []byte) bool {
if l := len(publicKey); l != PublicKeySize {
panic("ed25519: bad public key length: " + strconv.Itoa(l))
}
if len(sig) != SignatureSize || sig[63]&224 != 0 {
return false
}
var A edwards25519.ExtendedGroupElement
var publicKeyBytes [32]byte
copy(publicKeyBytes[:], publicKey)
if !A.FromBytes(&publicKeyBytes) {
return false
}
edwards25519.FeNeg(&A.X, &A.X)
edwards25519.FeNeg(&A.T, &A.T)
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
}
