/* 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);
}
/* Galbraith & Scott Method */
public static BIG[] gs(BIG e)
{
int i, j;
BIG t = new BIG(0);
BIG q = new BIG(ROM.CURVE_Order);
BIG[] u = new BIG[4];
BIG[] v = new BIG[4];
for (i = 0; i < 4; i++)
{
t.copy(new BIG(ROM.CURVE_WB[i]));
DBIG d = BIG.mul(t, e);
v[i] = new BIG(d.div(q));
u[i] = new BIG(0);
}
u[0].copy(e);
for (i = 0; i < 4; i++)
{
for (j = 0; j < 4; j++)
{
t.copy(new BIG(ROM.CURVE_BB[j][i]));
t.copy(BIG.modmul(v[j], t, q));
u[i].add(q);
u[i].sub(t);
u[i].mod(q);
}
}
return(u);
}
/* GLV method */
public static BIG[] glv(BIG e)
{
int i, j;
BIG t = new BIG(0);
BIG q = new BIG(ROM.CURVE_Order);
BIG[] u = new BIG[2];
BIG[] v = new BIG[2];
for (i = 0; i < 2; i++)
{
t.copy(new BIG(ROM.CURVE_W[i])); // why not just t=new BIG(ROM.CURVE_W[i]);
DBIG d = BIG.mul(t, e);
v[i] = new BIG(d.div(q));
u[i] = new BIG(0);
}
u[0].copy(e);
for (i = 0; i < 2; i++)
{
for (j = 0; j < 2; j++)
{
t.copy(new BIG(ROM.CURVE_SB[j][i]));
t.copy(BIG.modmul(v[j], t, q));
u[i].add(q);
u[i].sub(t);
u[i].mod(q);
}
}
return(u);
}
/* 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);
}
