int eb_is_valid(const eb_t p) { eb_t t; fb_t lhs; int r = 0; eb_null(t); fb_null(lhs); TRY { eb_new(t); fb_new(lhs); eb_norm(t, p); fb_mul(lhs, t->x, t->y); eb_rhs(t->x, t); fb_sqr(t->y, t->y); fb_add(lhs, lhs, t->y); r = (fb_cmp(lhs, t->x) == CMP_EQ) || eb_is_infty(p); } CATCH_ANY { THROW(ERR_CAUGHT); } FINALLY { eb_free(t); fb_free(lhs); } return r; }
int eb_upk(eb_t r, const eb_t p) { fb_t t0, t1; int res = 0; fb_null(t0); fb_null(t1); TRY { fb_new(t0); fb_new(t1); eb_rhs(t1, p); if (eb_curve_is_super()) { /* t0 = c^2. */ fb_sqr(t0, eb_curve_get_c()); /* t0 = 1/c^2. */ fb_inv(t0, t0); /* t0 = t1/c^2. */ fb_mul(t0, t0, t1); res = (fb_trc(t0) == 0); /* Solve t1^2 + t1 = t0. */ fb_slv(t1, t0); /* If this is not the correct solution, try the other. */ if (fb_get_bit(t1, 0) != fb_get_bit(p->y, 0)) { fb_add_dig(t1, t1, 1); } /* x3 = x1, y3 = t1 * c, z3 = 1. */ fb_mul(r->y, t1, eb_curve_get_c()); } else { fb_sqr(t0, p->x); /* t0 = 1/x1^2. */ fb_inv(t0, t0); /* t0 = t1/x1^2. */ fb_mul(t0, t0, t1); res = (fb_trc(t0) == 0); /* Solve t1^2 + t1 = t0. */ fb_slv(t1, t0); /* If this is not the correct solution, try the other. */ if (fb_get_bit(t1, 0) != fb_get_bit(p->y, 0)) { fb_add_dig(t1, t1, 1); } /* x3 = x1, y3 = t1 * x1, z3 = 1. */ fb_mul(r->y, t1, p->x); } fb_copy(r->x, p->x); fb_set_dig(r->z, 1); r->norm = 1; } CATCH_ANY { THROW(ERR_CAUGHT); } FINALLY { fb_free(t0); fb_free(t1); } return res; }