inistal commit

xifrat.go

@@ -0,0 +1,196 @@
+package goxifrat
+
+import (
+	"crypto"
+	"crypto/subtle"
+	"strconv"
+	//"crypto/sha512"
+	"errors"
+	"io"
+)
+
+const (
+	P = 16
+	N = 64
+	R = 64
+)
+
+var st = [P][P]uint8{
+	{7, 9, 13, 10, 15, 2, 0, 6, 3, 12, 8, 4, 1, 5, 14, 11},
+	{1, 15, 6, 3, 9, 4, 11, 13, 10, 5, 14, 2, 7, 12, 8, 0},
+	{3, 0, 12, 1, 11, 8, 9, 5, 7, 13, 2, 14, 10, 6, 4, 15},
+	{4, 6, 15, 8, 13, 1, 5, 9, 14, 11, 10, 7, 2, 0, 3, 12},
+	{0, 3, 8, 15, 10, 12, 7, 14, 9, 2, 13, 5, 11, 4, 6, 1},
+	{10, 11, 5, 7, 0, 14, 15, 12, 1, 6, 4, 8, 3, 13, 2, 9},
+	{5, 14, 10, 13, 8, 11, 4, 3, 6, 1, 15, 0, 12, 7, 9, 2},
+	{15, 1, 4, 0, 7, 6, 10, 2, 11, 14, 5, 13, 9, 8, 12, 3},
+	{12, 8, 3, 6, 14, 0, 2, 10, 13, 7, 9, 11, 5, 1, 15, 4},
+	{13, 2, 7, 5, 4, 9, 8, 1, 12, 3, 0, 15, 6, 10, 11, 14},
+	{6, 4, 1, 12, 2, 15, 14, 7, 5, 10, 11, 9, 13, 3, 0, 8},
+	{9, 7, 2, 11, 1, 13, 3, 4, 0, 8, 12, 6, 15, 14, 5, 10},
+	{11, 10, 14, 9, 3, 5, 1, 8, 15, 4, 6, 12, 0, 2, 13, 7},
+	{14, 5, 11, 2, 12, 10, 6, 0, 4, 15, 1, 3, 8, 9, 7, 13},
+	{8, 12, 0, 4, 5, 3, 13, 11, 2, 9, 7, 10, 14, 15, 1, 6},
+	{2, 13, 9, 14, 6, 7, 12, 15, 8, 0, 3, 1, 4, 11, 10, 5},
+}
+
+func m(a, b [N]uint8) (r [N]uint8) {
+	for j := 0; j < N; j++ {
+		r[j] = st[a[j]][b[j]]
+	}
+	e := rn[0]
+	for i := 0; i < R*N; i++ {
+		d := rn[i+1]
+		r[d] = st[r[d]][r[e]]
+		e = d
+	}
+	for j := 0; j < N; j++ {
+		r[j] = st[r[j]][b[j]]
+	}
+	return
+}
+
+type KeyAgreement struct {
+	P    [N]uint8
+	C    [N]uint8
+	S1   [N]uint8
+	S2   [N]uint8
+	init bool
+}
+
+func NewKeyAgreement(random io.Reader) (k *KeyAgreement, err error) {
+	p, err := randomArray(random)
+	if err != nil {
+		return nil, err
+	}
+	return &KeyAgreement{P: p}, nil
+}
+
+func (k *KeyAgreement) InitPhase(random io.Reader) (b []byte, err error) {
+	k.C, err = randomArray(random)
+	if err != nil {
+		return
+	}
+	k.S1 = m(k.C, k.P)
+	k.S2 = m(k.P, k.C)
+	b = append(b, encode(k.C)...)
+	b = append(b, encode(k.S1)...)
+	k.init = true
+	return
+}
+
+func (k *KeyAgreement) SharedSecret(buf []byte) (sec, b []byte, err error) {
+	if !k.init {
+		if l := len(buf); l != 64 {
+			return nil, nil, errors.New("xifrat: bad buffer length: " + strconv.Itoa(l))
+		}
+		k.C = decode(buf[:32])
+		buf = buf[32:]
+		k.S1 = m(k.C, k.P)
+		k.S2 = m(k.P, k.C)
+		k.init = true
+	}
+	if l := len(buf); l != KeySize {
+		return nil, nil, errors.New("xifrat: bad buffer length: " + strconv.Itoa(l))
+	}
+	b = encode(k.S1)
+	sec = encode(m(decode(buf), k.S2))
+	return
+}
+
+func encode(a [N]uint8) (buf []byte) {
+	buf = make([]byte, len(a)/2)
+	c := 0
+	for i := 0; i < len(a); i++ {
+		b := byte(a[i])
+		i++
+		buf[c] = (b << 4) | a[i]
+		c++
+	}
+	return
+}
+
+const (
+	KeySize = 32
+	SigSize = 96
+)
+
+func decode(buf []byte) (a [N]uint8) {
+	c := 0
+	for _, b := range buf {
+		a[c] = uint8(b >> 4)
+		c++
+		a[c] = uint8((b << 4) >> 4)
+		c++
+	}
+	return
+}
+
+type PublicKey struct {
+	C [N]uint8
+}
+
+type PrivateKey struct {
+	PublicKey
+	Q [N]uint8
+}
+
+func (priv *PrivateKey) Public() crypto.PublicKey {
+	return &priv.PublicKey
+}
+
+func (priv *PrivateKey) Sign(random io.Reader, digest []byte) (sig []byte, err error) {
+	if l := len(digest); l != KeySize {
+		return nil, errors.New("xifrat: bad digest length: " + strconv.Itoa(l))
+	}
+	k, err := randomArray(random)
+	if err != nil {
+		return
+	}
+	hash := decode(digest)
+	s := m(hash, priv.Q)
+	ck := m(priv.PublicKey.C, k)
+	qk := m(priv.Q, k)
+	sig = append(sig, encode(s)...)
+	sig = append(sig, encode(ck)...)
+	sig = append(sig, encode(qk)...)
+	return
+}
+
+func Verify(pub *PublicKey, digest, sig []byte) bool {
+	if l := len(digest); l != KeySize {
+		panic("xifrat: bad digest length: " + strconv.Itoa(l))
+	}
+	if l := len(sig); l != SigSize {
+		panic("xifrat: bad signature length: " + strconv.Itoa(l))
+	}
+	s := decode(sig[:32])
+	ck := decode(sig[32:64])
+	qk := decode(sig[64:96])
+	hash := decode(digest)
+	v1 := m(s, ck)
+	v2 := m(m(hash, pub.C), qk)
+	return subtle.ConstantTimeCompare(encode(v1), encode(v2)) == 1
+}
+
+func randomArray(random io.Reader) (a [N]uint8, err error) {
+	buf := make([]byte, 32)
+	_, err = random.Read(buf)
+	if err != nil {
+		return
+	}
+	a = decode(buf)
+	return
+}
+
+func GenerateKey(random io.Reader) (p *PrivateKey, err error) {
+	pub, err := randomArray(random)
+	if err != nil {
+		return nil, err
+	}
+	priv, err := randomArray(random)
+	if err != nil {
+		return nil, err
+	}
+	return &PrivateKey{PublicKey{pub}, priv}, nil
+}