/* constant time multiply by small integer of length bts - use ladder */
public ECP pinmul(int e, int bts)
{
if (ROM.CURVETYPE == ROM.MONTGOMERY)
{
return(this.mul(new BIG(e)));
}
else
{
int nb, i, b;
ECP P = new ECP();
ECP R0 = new ECP();
ECP R1 = new ECP();
R1.copy(this);
for (i = bts - 1; i >= 0; i--)
{
b = (e >> i) & 1;
P.copy(R1);
P.add(R0);
R0.cswap(R1, b);
R1.copy(P);
R0.dbl();
R0.cswap(R1, b);
}
P.copy(R0);
P.affine();
return(P);
}
}
/* IEEE1363 ECDSA Signature Verification. Signature C and D on F is verified using public key W */
public static int ECPVP_DSA(sbyte[] W, sbyte[] F, sbyte[] C, sbyte[] D)
{
BIG r, gx, gy, f, c, d, h2;
int res = 0;
ECP G, WP, P;
HASH H = new HASH();
H.process_array(F);
sbyte[] B = H.hash();
gx = new BIG(ROM.CURVE_Gx);
gy = new BIG(ROM.CURVE_Gy);
G = new ECP(gx, gy);
r = new BIG(ROM.CURVE_Order);
c = BIG.fromBytes(C);
d = BIG.fromBytes(D);
f = BIG.fromBytes(B);
if (c.iszilch() || BIG.comp(c, r) >= 0 || d.iszilch() || BIG.comp(d, r) >= 0)
{
res = INVALID;
}
if (res == 0)
{
d.invmodp(r);
f.copy(BIG.modmul(f, d, r));
h2 = BIG.modmul(c, d, r);
WP = ECP.fromBytes(W);
if (WP.is_infinity())
{
res = ERROR;
}
else
{
P = new ECP();
P.copy(WP);
P = P.mul2(h2, G, f);
if (P.is_infinity())
{
res = INVALID;
}
else
{
d = P.X;
d.mod(r);
if (BIG.comp(d, c) != 0)
{
res = INVALID;
}
}
}
}
return(res);
}
/* IEEE ECDSA Signature, C and D are signature on F using private key S */
public static int ECPSP_DSA(RAND RNG, sbyte[] S, sbyte[] F, sbyte[] C, sbyte[] D)
{
sbyte[] T = new sbyte[EFS];
BIG gx, gy, r, s, f, c, d, u, vx;
ECP G, V;
HASH H = new HASH();
H.process_array(F);
sbyte[] B = H.hash();
gx = new BIG(ROM.CURVE_Gx);
gy = new BIG(ROM.CURVE_Gy);
G = new ECP(gx, gy);
r = new BIG(ROM.CURVE_Order);
s = BIG.fromBytes(S);
f = BIG.fromBytes(B);
c = new BIG(0);
d = new BIG(0);
V = new ECP();
do
{
u = BIG.randomnum(r, RNG);
V.copy(G);
V = V.mul(u);
vx = V.X;
c.copy(vx);
c.mod(r);
if (c.iszilch())
{
continue;
}
u.invmodp(r);
d.copy(BIG.modmul(s, c, r));
d.add(f);
d.copy(BIG.modmul(u, d, r));
} while (d.iszilch());
c.toBytes(T);
for (int i = 0; i < EFS; i++)
{
C[i] = T[i];
}
d.toBytes(T);
for (int i = 0; i < EFS; i++)
{
D[i] = T[i];
}
return(0);
}
/* Multiply P by e in group G1 */
public static ECP G1mul(ECP P, BIG e)
{
ECP R;
if (ROM.USE_GLV)
{
P.affine();
R = new ECP();
R.copy(P);
int i, np, nn;
ECP Q = new ECP();
Q.copy(P);
BIG q = new BIG(ROM.CURVE_Order);
FP cru = new FP(new BIG(ROM.CURVE_Cru));
BIG t = new BIG(0);
BIG[] u = glv(e);
Q.getx().mul(cru);
np = u[0].nbits();
t.copy(BIG.modneg(u[0], q));
nn = t.nbits();
if (nn < np)
{
u[0].copy(t);
R.neg();
}
np = u[1].nbits();
t.copy(BIG.modneg(u[1], q));
nn = t.nbits();
if (nn < np)
{
u[1].copy(t);
Q.neg();
}
R = R.mul2(u[0], Q, u[1]);
}
else
{
R = P.mul(e);
}
return(R);
}
/* Constant time select from pre-computed table */
private void select(ECP[] W, int b)
{
ECP MP = new ECP();
int m = b >> 31;
int babs = (b ^ m) - m;
babs = (babs - 1) / 2;
cmove(W[0], teq(babs, 0)); // conditional move
cmove(W[1], teq(babs, 1));
cmove(W[2], teq(babs, 2));
cmove(W[3], teq(babs, 3));
cmove(W[4], teq(babs, 4));
cmove(W[5], teq(babs, 5));
cmove(W[6], teq(babs, 6));
cmove(W[7], teq(babs, 7));
MP.copy(this);
MP.neg();
cmove(MP, (int)(m & 1));
}
/* return e.this */
public ECP mul(BIG e)
{
if (e.iszilch() || is_infinity())
{
return(new ECP());
}
ECP P = new ECP();
if (ROM.CURVETYPE == ROM.MONTGOMERY)
{
/* use Ladder */
int nb, i, b;
ECP D = new ECP();
ECP R0 = new ECP();
R0.copy(this);
ECP R1 = new ECP();
R1.copy(this);
R1.dbl();
D.copy(this);
D.affine();
nb = e.nbits();
for (i = nb - 2; i >= 0; i--)
{
b = e.bit(i);
P.copy(R1);
P.dadd(R0, D);
R0.cswap(R1, b);
R1.copy(P);
R0.dbl();
R0.cswap(R1, b);
}
P.copy(R0);
}
else
{
// fixed size windows
int i, b, nb, m, s, ns;
BIG mt = new BIG();
BIG t = new BIG();
ECP Q = new ECP();
ECP C = new ECP();
ECP[] W = new ECP[8];
sbyte[] w = new sbyte[1 + (ROM.NLEN * ROM.BASEBITS + 3) / 4];
affine();
// precompute table
Q.copy(this);
Q.dbl();
W[0] = new ECP();
W[0].copy(this);
for (i = 1; i < 8; i++)
{
W[i] = new ECP();
W[i].copy(W[i - 1]);
W[i].add(Q);
}
// convert the table to affine
if (ROM.CURVETYPE == ROM.WEIERSTRASS)
{
multiaffine(8, W);
}
// make exponent odd - add 2P if even, P if odd
t.copy(e);
s = t.parity();
t.inc(1);
t.norm();
ns = t.parity();
mt.copy(t);
mt.inc(1);
mt.norm();
t.cmove(mt, s);
Q.cmove(this, ns);
C.copy(Q);
nb = 1 + (t.nbits() + 3) / 4;
// convert exponent to signed 4-bit window
for (i = 0; i < nb; i++)
{
w[i] = (sbyte)(t.lastbits(5) - 16);
t.dec(w[i]);
t.norm();
t.fshr(4);
}
w[nb] = (sbyte)t.lastbits(5);
P.copy(W[(w[nb] - 1) / 2]);
for (i = nb - 1; i >= 0; i--)
{
Q.select(W, w[i]);
P.dbl();
P.dbl();
P.dbl();
P.dbl();
P.add(Q);
}
P.sub(C); // apply correction
}
P.affine();
return(P);
}
/* Return e.this+f.Q */
public ECP mul2(BIG e, ECP Q, BIG f)
{
BIG te = new BIG();
BIG tf = new BIG();
BIG mt = new BIG();
ECP S = new ECP();
ECP T = new ECP();
ECP C = new ECP();
ECP[] W = new ECP[8];
sbyte[] w = new sbyte[1 + (ROM.NLEN * ROM.BASEBITS + 1) / 2];
int i, s, ns, nb;
sbyte a, b;
affine();
Q.affine();
te.copy(e);
tf.copy(f);
// precompute table
W[1] = new ECP();
W[1].copy(this);
W[1].sub(Q);
W[2] = new ECP();
W[2].copy(this);
W[2].add(Q);
S.copy(Q);
S.dbl();
W[0] = new ECP();
W[0].copy(W[1]);
W[0].sub(S);
W[3] = new ECP();
W[3].copy(W[2]);
W[3].add(S);
T.copy(this);
T.dbl();
W[5] = new ECP();
W[5].copy(W[1]);
W[5].add(T);
W[6] = new ECP();
W[6].copy(W[2]);
W[6].add(T);
W[4] = new ECP();
W[4].copy(W[5]);
W[4].sub(S);
W[7] = new ECP();
W[7].copy(W[6]);
W[7].add(S);
// convert the table to affine
if (ROM.CURVETYPE == ROM.WEIERSTRASS)
{
multiaffine(8, W);
}
// if multiplier is odd, add 2, else add 1 to multiplier, and add 2P or P to correction
s = te.parity();
te.inc(1);
te.norm();
ns = te.parity();
mt.copy(te);
mt.inc(1);
mt.norm();
te.cmove(mt, s);
T.cmove(this, ns);
C.copy(T);
s = tf.parity();
tf.inc(1);
tf.norm();
ns = tf.parity();
mt.copy(tf);
mt.inc(1);
mt.norm();
tf.cmove(mt, s);
S.cmove(Q, ns);
C.add(S);
mt.copy(te);
mt.add(tf);
mt.norm();
nb = 1 + (mt.nbits() + 1) / 2;
// convert exponent to signed 2-bit window
for (i = 0; i < nb; i++)
{
a = (sbyte)(te.lastbits(3) - 4);
te.dec(a);
te.norm();
te.fshr(2);
b = (sbyte)(tf.lastbits(3) - 4);
tf.dec(b);
tf.norm();
tf.fshr(2);
w[i] = (sbyte)(4 * a + b);
}
w[nb] = (sbyte)(4 * te.lastbits(3) + tf.lastbits(3));
S.copy(W[(w[nb] - 1) / 2]);
for (i = nb - 1; i >= 0; i--)
{
T.select(W, w[i]);
S.dbl();
S.dbl();
S.add(T);
}
S.sub(C); // apply correction
S.affine();
return(S);
}
