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tls: P256: remove constant-time trick in sp_256_proj_point_add_8

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function                                             old     new   delta
sp_256_proj_point_add_8                              576     544     -32

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2021-11-27 15:06:57 +01:00
parent 26c8522522
commit bbda85c74b
1 changed files with 36 additions and 41 deletions
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77
networking/tls_sp_c32.c
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@@ -1269,52 +1269,47 @@ static NOINLINE void sp_256_proj_point_add_8(sp_point* r, sp_point* p, sp_point*
&& (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.