int cp_bgn_dec1(dig_t *out, g1_t in[2], bgn_t prv) {
bn_t r, n;
g1_t s, t, u;
int i, result = STS_ERR;
bn_null(n);
bn_null(r);
g1_null(s);
g1_null(t);
g1_null(u);
TRY {
bn_new(n);
bn_new(r);
g1_new(s);
g1_new(t);
g1_new(u);
g1_get_ord(n);
/* Compute T = x(ym + r)G - (zm + xr)G = m(xy - z)G. */
g1_mul(t, in[0], prv->x);
g1_sub(t, t, in[1]);
g1_norm(t, t);
/* Compute U = (xy - z)G and find m. */
bn_mul(r, prv->x, prv->y);
bn_sub(r, r, prv->z);
bn_mod(r, r, n);
g1_mul_gen(s, r);
g1_copy(u, s);
if (g1_is_infty(t) == 1){
*out = 0;
result = STS_OK;
} else {
for (i = 0; i < INT_MAX; i++) {
if (g1_cmp(t, u) == CMP_EQ) {
*out = i + 1;
result = STS_OK;
break;
}
g1_add(u, u, s);
g1_norm(u, u);
}
}
} CATCH_ANY {
result = STS_ERR;
}
FINALLY {
bn_free(n);
bn_free(r);
g1_free(s);
g1_free(t);
g1_free(u);
}
return result;
}
int element_cmp(element_t a, element_t b)
{
GroupType type = a->type;
LEAVE_IF(a->isInitialized != TRUE || b->isInitialized != TRUE, "uninitialized argument.");
EXIT_IF_NOT_SAME(a, b);
switch(type) {
case ZR: return bn_cmp(a->bn, b->bn);
case G1: return g1_cmp(a->g1, b->g1);
case G2: return g2_cmp(a->g2, b->g2);
case GT: return gt_cmp(a->gt, b->gt);
default: break;
}
return ELEMENT_INVALID_TYPES;
}
