status_t element_sub(element_t c, element_t a, element_t b)
{
GroupType type = a->type;
EXIT_IF_NOT_SAME(a, b);
LEAVE_IF(a->isInitialized != TRUE || b->isInitialized != TRUE, "uninitialized arguments.");
LEAVE_IF( c->type != type, "result initialized but invalid type.");
if(type == ZR) {
bn_sub(c->bn, a->bn, b->bn);
bn_mod(c->bn, c->bn, c->order);
}
else if(type == G1) {
g1_sub(c->g1, a->g1, b->g1);
g1_norm(c->g1, c->g1);
}
else if(type == G2) {
g2_sub(c->g2, a->g2, b->g2);
g2_norm(c->g2, c->g2);
}
else {
return ELEMENT_INVALID_TYPES;
}
return ELEMENT_OK;
}
int cp_bgn_dec2(dig_t *out, g2_t in[2], bgn_t prv) {
bn_t r, n;
g2_t s, t, u;
int i, result = STS_ERR;
bn_null(n);
bn_null(r);
g2_null(s);
g2_null(t);
g2_null(u);
TRY {
bn_new(n);
bn_new(r);
g2_new(s);
g2_new(t);
g2_new(u);
g2_get_ord(n);
/* Compute T = x(ym + r)G - (zm + xr)G = m(xy - z)G. */
g2_mul(t, in[0], prv->x);
g2_sub(t, t, in[1]);
g2_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);
g2_mul_gen(s, r);
g2_copy(u, s);
if (g2_is_infty(t) == 1) {
*out = 0;
result = STS_OK;
} else {
for (i = 0; i < INT_MAX; i++) {
if (g2_cmp(t, u) == CMP_EQ) {
*out = i + 1;
result = STS_OK;
break;
}
g2_add(u, u, s);
g2_norm(u, u);
}
}
} CATCH_ANY {
result = STS_ERR;
}
FINALLY {
bn_free(n);
bn_free(r);
g2_free(s);
g2_free(t);
g2_free(u);
}
return result;
}
status_t element_div(element_t c, element_t a, element_t b)
{
GroupType type = a->type;
EXIT_IF_NOT_SAME(a, b);
LEAVE_IF(a->isInitialized != TRUE || b->isInitialized != TRUE || c->isInitialized != TRUE, "uninitialized arguments.");
LEAVE_IF( c->type != type, "result initialized but invalid type.");
if(type == ZR) {
if(bn_is_zero(b->bn)) return ELEMENT_DIV_ZERO;
// c = (1 / b) mod order
element_invert(c, b);
if(bn_is_one(a->bn)) return ELEMENT_OK;
// bn_div(c->bn, a->bn, b->bn);
// bn_mod(c->bn, c->bn, c->order);
// remainder of ((a * c) / order)
integer_t s;
bn_inits(s);
// c = (a * c) / order (remainder only)
bn_mul(s, a->bn, c->bn);
bn_div_rem(s, c->bn, s, a->order);
// if(bn_sign(c->bn) == BN_NEG) bn_add(c->bn, c->bn, a->order);
bn_free(s);
}
else if(type == G1) {
g1_sub(c->g1, a->g1, b->g1);
g1_norm(c->g1, c->g1);
}
else if(type == G2) {
g2_sub(c->g2, a->g2, b->g2);
g2_norm(c->g2, c->g2);
}
else if(type == GT) {
gt_t t;
gt_inits(t);
gt_inv(t, b->gt);
gt_mul(c->gt, a->gt, t);
gt_free(t);
}
else {
return ELEMENT_INVALID_TYPES;
}
return ELEMENT_OK;
}
