/* Returns the appropriate base-two padded
bytes (assuming the underlying big representation
remains b2c) */
func BigBytes(i *big.Int) (buff []byte) {
ib := i.Bytes()
shift := 0
shiftbyte := byte(0)
switch i.Cmp(big.NewInt(0)) {
case 1:
// Positive must be padded if high-bit is 1
if ib[0]&0x80 == 0x80 {
shift = 1
}
case -1:
// Negative numbers with a leading high-bit will also need
// to be padded, but with a single bit tagging its 'negativity'
if ib[0]&0x80 == 0x80 {
shift = 1
shiftbyte = 0x80
}
}
buff = make([]byte, len(ib)+shift)
if shift == 1 {
buff[0] = shiftbyte
}
copy(buff[shift:], ib)
return
}
func (h *Hash) l3(m []byte, iter int) []byte {
i := 0
k1 := new(big.Int)
k2 := new(big.Int)
for need := iter + 1; need > 0; i++ {
t := h.kdf(224, 128*(i+1))[16*i : 16*(i+1)]
k1.SetBytes(t[:8])
k2.SetBytes(t[8:])
if k1.Cmp(p64) == -1 && k2.Cmp(p64) == -1 {
need--
}
}
mint := newInt(m)
m1 := new(big.Int).Div(mint, p64p32)
m2 := new(big.Int).Mod(mint, p64p32)
y := new(big.Int).Add(m1, k1)
y.Mul(y, new(big.Int).Add(m2, k2))
y.Mod(y, p64)
Y := make([]byte, 8)
copy(Y[8-len(y.Bytes()):], y.Bytes())
return Y
}
// Sign signs an arbitrary length hash (which should be the result of hashing a
// larger message) using the private key, priv. It returns the signature as a
// pair of integers. The security of the private key depends on the entropy of
// rand.
func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err os.Error) {
// See [NSA] 3.4.1
c := priv.PublicKey.Curve
var k, kInv *big.Int
for {
for {
k, err = randFieldElement(c, rand)
if err != nil {
r = nil
return
}
kInv = new(big.Int).ModInverse(k, c.N)
r, _ = priv.Curve.ScalarBaseMult(k.Bytes())
r.Mod(r, priv.Curve.N)
if r.Sign() != 0 {
break
}
}
e := hashToInt(hash, c)
s = new(big.Int).Mul(priv.D, r)
s.Add(s, e)
s.Mul(s, kInv)
s.Mod(s, priv.PublicKey.Curve.N)
if s.Sign() != 0 {
break
}
}
return
}
// Decrypt takes two integers, resulting from an ElGamal encryption, and
// returns the plaintext of the message. An error can result only if the
// ciphertext is invalid. Users should keep in mind that this is a padding
// oracle and thus, if exposed to an adaptive chosen ciphertext attack, can
// be used to break the cryptosystem. See ``Chosen Ciphertext Attacks
// Against Protocols Based on the RSA Encryption Standard PKCS #1'', Daniel
// Bleichenbacher, Advances in Cryptology (Crypto '98),
func Decrypt(priv *PrivateKey, c1, c2 *big.Int) (msg []byte, err error) {
s := new(big.Int).Exp(c1, priv.X, priv.P)
s.ModInverse(s, priv.P)
s.Mul(s, c2)
s.Mod(s, priv.P)
em := s.Bytes()
firstByteIsTwo := subtle.ConstantTimeByteEq(em[0], 2)
// The remainder of the plaintext must be a string of non-zero random
// octets, followed by a 0, followed by the message.
// lookingForIndex: 1 iff we are still looking for the zero.
// index: the offset of the first zero byte.
var lookingForIndex, index int
lookingForIndex = 1
for i := 1; i < len(em); i++ {
equals0 := subtle.ConstantTimeByteEq(em[i], 0)
index = subtle.ConstantTimeSelect(lookingForIndex&equals0, i, index)
lookingForIndex = subtle.ConstantTimeSelect(equals0, 0, lookingForIndex)
}
if firstByteIsTwo != 1 || lookingForIndex != 0 || index < 9 {
return nil, errors.New("elgamal: decryption error")
}
return em[index+1:], nil
}
func (curve *Curve) Multiply(n *big.Int, p *Point) *Point {
if p == nil {
//fmt.Printf("p == nil!?wtfbbq\n")
return p
}
bytes := n.Bytes()
length := len(bytes)
bitlength := length * 8
fmt.Printf("length = %d\n", bitlength)
var rightmost uint = 0x01
//fmt.Printf("leftmost = %d\n", leftmost)
p2 := p
last_i := bitlength - 1
var ptotal *Point
ptotal = nil
for i := bitlength - 1; i >= 0; i-- {
//fmt.Printf("\n(i mod 8) = %d \n", 7-(i%8))
if uint(rightmost<<uint(7-(i%8)))&uint(bytes[i/8]) != 0 {
for j := last_i; j > i; j-- {
//fmt.Printf("Doubling! i=%d\n",i)
p2 = curve.double(p2)
}
last_i = i
fmt.Printf("last_i = %d\n", last_i)
ptotal = curve.Add(p2, ptotal)
}
}
return ptotal
}
// Vygeneruje "nahodne" nenulove cislo mensi nez n
func RandNumSmaller(n *big.Int) (r *big.Int) {
r = big.NewInt(0)
for r.Cmp(big0) == 0 {
bytes := randBytes(len(n.Bytes()) * 8)
r.SetBytes(bytes)
r.Mod(r, n)
}
return
}
// Set the public key (the value E and N)
func (k *RR_DNSKEY) setPublicKeyRSA(_E int, _N *big.Int) bool {
if _E == 0 || _N == nil {
return false
}
buf := exponentToBuf(_E)
buf = append(buf, _N.Bytes()...)
k.PublicKey = unpackBase64(buf)
return true
}
func BenchmarkBaseMult(b *testing.B) {
b.ResetTimer()
p224 := P224()
e := p224BaseMultTests[25]
k, _ := new(big.Int).SetString(e.k, 10)
b.StartTimer()
for i := 0; i < b.N; i++ {
p224.ScalarBaseMult(k.Bytes())
}
}
//TODO: test more curves?
func BenchmarkBaseMult(b *testing.B) {
b.ResetTimer()
s256 := S224()
e := s256BaseMultTests[0] //TODO: check, used to be 25 instead of 0, but it's probably ok
k, _ := new(big.Int).SetString(e.k, 16)
b.StartTimer()
for i := 0; i < b.N; i++ {
s256.ScalarBaseMult(k.Bytes())
}
}
// rawValueForBig returns an asn1.RawValue which represents the given integer.
func rawValueForBig(n *big.Int) asn1.RawValue {
b := n.Bytes()
if n.Sign() >= 0 && len(b) > 0 && b[0]&0x80 != 0 {
// This positive number would be interpreted as a negative
// number in ASN.1 because the MSB is set.
padded := make([]byte, len(b)+1)
copy(padded[1:], b)
b = padded
}
return asn1.RawValue{Tag: 2, Bytes: b}
}
// Marshal converts a point into the form specified in section 4.3.6 of ANSI
// X9.62.
func (curve *Curve) Marshal(x, y *big.Int) []byte {
byteLen := (curve.BitSize + 7) >> 3
ret := make([]byte, 1+2*byteLen)
ret[0] = 4 // uncompressed point
xBytes := x.Bytes()
copy(ret[1+byteLen-len(xBytes):], xBytes)
yBytes := y.Bytes()
copy(ret[1+2*byteLen-len(yBytes):], yBytes)
return ret
}
func (h *Hash) Sum() []byte {
hashed := h.vhash()
pad := h.pdf()
sum := make([]byte, h.size)
for i := 0; i < h.size/8; i++ {
lo := 8 * i
hi := 8 * (i + 1)
t := new(big.Int).Add(newInt(pad[lo:hi]), newInt(hashed[lo:hi]))
t.Mod(t, m64)
copy(sum[hi-len(t.Bytes()):hi], t.Bytes())
}
return sum
}
//TODO: check
func Big2Hex32(b *big.Int) [32]byte {
var answer [32]byte
tmp := b.Bytes()
if len(tmp) <= 32 {
for i := 0; i < len(tmp); i++ {
answer[31-i] = tmp[i]
}
}
return answer
}
func TestBaseMult(t *testing.T) {
p224 := P224()
for i, e := range p224BaseMultTests {
k, ok := new(big.Int).SetString(e.k, 10)
if !ok {
t.Errorf("%d: bad value for k: %s", i, e.k)
}
x, y := p224.ScalarBaseMult(k.Bytes())
if fmt.Sprintf("%x", x) != e.x || fmt.Sprintf("%x", y) != e.y {
t.Errorf("%d: bad output for k=%s: got (%x, %s), want (%s, %s)", i, e.k, x, y, e.x, e.y)
}
}
}
//TODO: test different curves as well?
func TestBaseMult(t *testing.T) {
s256 := S256()
for i, e := range s256BaseMultTests {
k, ok := new(big.Int).SetString(e.k, 16)
if !ok {
t.Errorf("%d: bad value for k: %s", i, e.k)
}
x, y := s256.ScalarBaseMult(k.Bytes())
if fmt.Sprintf("%X", x) != e.x || fmt.Sprintf("%X", y) != e.y {
t.Errorf("%d: bad output for k=%s: got (%X, %X), want (%s, %s)", i, e.k, x, y, e.x, e.y)
}
if testing.Short() && i > 5 {
break
}
}
}
func marshalInt(to []byte, n *big.Int) []byte {
lengthBytes := to
to = to[4:]
length := 0
if n.Sign() < 0 {
// A negative number has to be converted to two's-complement
// form. So we'll subtract 1 and invert. If the
// most-significant-bit isn't set then we'll need to pad the
// beginning with 0xff in order to keep the number negative.
nMinus1 := new(big.Int).Neg(n)
nMinus1.Sub(nMinus1, bigOne)
bytes := nMinus1.Bytes()
for i := range bytes {
bytes[i] ^= 0xff
}
if len(bytes) == 0 || bytes[0]&0x80 == 0 {
to[0] = 0xff
to = to[1:]
length++
}
nBytes := copy(to, bytes)
to = to[nBytes:]
length += nBytes
} else if n.Sign() == 0 {
// A zero is the zero length string
} else {
bytes := n.Bytes()
if len(bytes) > 0 && bytes[0]&0x80 != 0 {
// We'll have to pad this with a 0x00 in order to
// stop it looking like a negative number.
to[0] = 0
to = to[1:]
length++
}
nBytes := copy(to, bytes)
to = to[nBytes:]
length += nBytes
}
lengthBytes[0] = byte(length >> 24)
lengthBytes[1] = byte(length >> 16)
lengthBytes[2] = byte(length >> 8)
lengthBytes[3] = byte(length)
return to
}
func marshalBigInt(out *forkableWriter, n *big.Int) (err os.Error) {
if n.Sign() < 0 {
// A negative number has to be converted to two's-complement
// form. So we'll subtract 1 and invert. If the
// most-significant-bit isn't set then we'll need to pad the
// beginning with 0xff in order to keep the number negative.
nMinus1 := new(big.Int).Neg(n)
nMinus1.Sub(nMinus1, bigOne)
bytes := nMinus1.Bytes()
for i := range bytes {
bytes[i] ^= 0xff
}
if len(bytes) == 0 || bytes[0]&0x80 == 0 {
err = out.WriteByte(0xff)
if err != nil {
return
}
}
_, err = out.Write(bytes)
} else if n.Sign() == 0 {
// Zero is written as a single 0 zero rather than no bytes.
err = out.WriteByte(0x00)
} else {
bytes := n.Bytes()
if len(bytes) > 0 && bytes[0]&0x80 != 0 {
// We'll have to pad this with 0x00 in order to stop it
// looking like a negative number.
err = out.WriteByte(0)
if err != nil {
return
}
}
_, err = out.Write(bytes)
}
return
}
// Set the public key for X and Y for Curve
// Experimental
func curveToBuf(_X, _Y *big.Int) []byte {
buf := _X.Bytes()
buf = append(buf, _Y.Bytes()...)
return buf
}
// Spocita msg^key % mod
func crypt(key, mod *big.Int, msg []byte) []byte {
a := new(big.Int).SetBytes(msg)
a.Exp(a, key, mod)
return a.Bytes()
}
func main() {
flag.Parse() // parsovani parametru prikazove radky
rand.Seed(time.Nanoseconds()) // inicializace generatoru nahodnych cisel
if *generateKeys {
SaveKeys(GenerateKeys(*keyLength))
}
// rozdeleni souboru na vice mensich podle delky klice
if *splitFile != "" {
rights := 0600
n, _ := ReadPublicKey()
bytes := readFile(*splitFile)
nl := len(n.Bytes()) - 1
i := 0
for ; i < len(bytes)/nl; i++ {
writeToFile(partfile(i), bytes[i*nl:(i+1)*nl], rights)
}
if len(bytes[i*nl:]) > 0 { // pokud deleni nevychazi presne
writeToFile(partfile(i), bytes[i*nl:], rights)
i++
}
// informacni soubor
writeToFile(*prefix+".info", strings.Bytes(fmt.Sprintf("%d", i)), rights)
}
// zasifruje/rozsifruje vsechny soubory verejnym klicem
if *encrypFiles {
n, e := ReadPublicKey()
max := msgscount()
for i := 0; i < max; i++ {
file := readFile(partfile(i))
bs := crypt(e, n, file)
writeToFile(partfile(i), bs, 0600)
}
}
// rozsifruje/zasifruje vsechny soubory soukromym klicem
if *decrypFiles {
p, q, d := ReadPrivateKey()
pinv := new(big.Int).Mul(p, invMod(p, q)) // = p*(p^-1 mod q)
qinv := new(big.Int).Mul(q, invMod(q, p)) // = q*(q^-1 mod p)
n := new(big.Int).Mul(p, q)
max := msgscount()
for i := 0; i < max; i++ {
file := readFile(partfile(i))
// CINSKA VETA O ZBYTCICH
bp := new(big.Int).SetBytes(crypt(d, p, file)) // decrypt mod p
bq := new(big.Int).SetBytes(crypt(d, q, file)) // decrypt mod q
// bs = bp * qinv + bq * binv (mod n)
bs := new(big.Int).Mul(bp, qinv)
bs.Add(bs, new(big.Int).Mul(bq, pinv))
bs.Mod(bs, n)
writeToFile(partfile(i), bs.Bytes(), 0600)
}
}
// spojeni souboru do jednoho
if *joinFile != "" {
max := msgscount()
var bs []byte
for i := 0; i < max; i++ {
file := readFile(partfile(i))
bs = bytes.Add(bs, file)
}
writeToFile(*joinFile, bs, 0600)
}
}
// writeBig serializes a *big.Int to w.
func writeBig(w io.Writer, i *big.Int) os.Error {
return writeMPI(w, uint16(i.BitLen()), i.Bytes())
}
func fromBig(n *big.Int) parsedMPI {
return parsedMPI{
bytes: n.Bytes(),
bitLength: uint16(n.BitLen()),
}
}
