tls: P256: remove constant-time trick in sp_256_proj_point_add_8
function old new delta
sp_256_proj_point_add_8 576 544 -32
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/tls_sp_c32.c b/networking/tls_sp_c32.c
index 29dd042..3b04730 100644
--- a/networking/tls_sp_c32.c
+++ b/networking/tls_sp_c32.c
@@ -1269,52 +1269,47 @@
&& (sp_256_cmp_equal_8(p->y, q->y) || sp_256_cmp_equal_8(p->y, t1))
) {
sp_256_proj_point_dbl_8(r, p);
+ return;
}
- else {
- sp_point tp;
- sp_point *v;
- v = r;
- if (p->infinity | q->infinity) {
- memset(&tp, 0, sizeof(tp));
- v = &tp;
- }
+ if (p->infinity || q->infinity) {
*r = p->infinity ? *q : *p; /* struct copy */
-
- /* U1 = X1*Z2^2 */
- sp_256_mont_sqr_8(t1, q->z /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(t3, t1, q->z /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(t1, t1, v->x /*, p256_mod, p256_mp_mod*/);
- /* U2 = X2*Z1^2 */
- sp_256_mont_sqr_8(t2, v->z /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(t4, t2, v->z /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(t2, t2, q->x /*, p256_mod, p256_mp_mod*/);
- /* S1 = Y1*Z2^3 */
- sp_256_mont_mul_8(t3, t3, v->y /*, p256_mod, p256_mp_mod*/);
- /* S2 = Y2*Z1^3 */
- sp_256_mont_mul_8(t4, t4, q->y /*, p256_mod, p256_mp_mod*/);
- /* H = U2 - U1 */
- sp_256_mont_sub_8(t2, t2, t1 /*, p256_mod*/);
- /* R = S2 - S1 */
- sp_256_mont_sub_8(t4, t4, t3 /*, p256_mod*/);
- /* Z3 = H*Z1*Z2 */
- sp_256_mont_mul_8(v->z, v->z, q->z /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(v->z, v->z, t2 /*, p256_mod, p256_mp_mod*/);
- /* X3 = R^2 - H^3 - 2*U1*H^2 */
- sp_256_mont_sqr_8(v->x, t4 /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_sqr_8(t5, t2 /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(v->y, t1, t5 /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(t5, t5, t2 /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_sub_8(v->x, v->x, t5 /*, p256_mod*/);
- sp_256_mont_dbl_8(t1, v->y /*, p256_mod*/);
- sp_256_mont_sub_8(v->x, v->x, t1 /*, p256_mod*/);
- /* Y3 = R*(U1*H^2 - X3) - S1*H^3 */
- sp_256_mont_sub_8(v->y, v->y, v->x /*, p256_mod*/);
- sp_256_mont_mul_8(v->y, v->y, t4 /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_mul_8(t5, t5, t3 /*, p256_mod, p256_mp_mod*/);
- sp_256_mont_sub_8(v->y, v->y, t5 /*, p256_mod*/);
+ return;
}
+
+ /* U1 = X1*Z2^2 */
+ sp_256_mont_sqr_8(t1, q->z /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(t3, t1, q->z /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(t1, t1, r->x /*, p256_mod, p256_mp_mod*/);
+ /* U2 = X2*Z1^2 */
+ sp_256_mont_sqr_8(t2, r->z /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(t4, t2, r->z /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(t2, t2, q->x /*, p256_mod, p256_mp_mod*/);
+ /* S1 = Y1*Z2^3 */
+ sp_256_mont_mul_8(t3, t3, r->y /*, p256_mod, p256_mp_mod*/);
+ /* S2 = Y2*Z1^3 */
+ sp_256_mont_mul_8(t4, t4, q->y /*, p256_mod, p256_mp_mod*/);
+ /* H = U2 - U1 */
+ sp_256_mont_sub_8(t2, t2, t1 /*, p256_mod*/);
+ /* R = S2 - S1 */
+ sp_256_mont_sub_8(t4, t4, t3 /*, p256_mod*/);
+ /* Z3 = H*Z1*Z2 */
+ sp_256_mont_mul_8(r->z, r->z, q->z /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(r->z, r->z, t2 /*, p256_mod, p256_mp_mod*/);
+ /* X3 = R^2 - H^3 - 2*U1*H^2 */
+ sp_256_mont_sqr_8(r->x, t4 /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_sqr_8(t5, t2 /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(r->y, t1, t5 /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(t5, t5, t2 /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_sub_8(r->x, r->x, t5 /*, p256_mod*/);
+ sp_256_mont_dbl_8(t1, r->y /*, p256_mod*/);
+ sp_256_mont_sub_8(r->x, r->x, t1 /*, p256_mod*/);
+ /* Y3 = R*(U1*H^2 - X3) - S1*H^3 */
+ sp_256_mont_sub_8(r->y, r->y, r->x /*, p256_mod*/);
+ sp_256_mont_mul_8(r->y, r->y, t4 /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_mul_8(t5, t5, t3 /*, p256_mod, p256_mp_mod*/);
+ sp_256_mont_sub_8(r->y, r->y, t5 /*, p256_mod*/);
}
/* Multiply the point by the scalar and return the result.