From bbda85c74b7a53d8b2bb46f3b44d8f0932a6e95d Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Sat, 27 Nov 2021 15:06:57 +0100 Subject: [PATCH] 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 --- networking/tls_sp_c32.c | 77 +++++++++++++++++++---------------------- 1 file changed, 36 insertions(+), 41 deletions(-) diff --git a/networking/tls_sp_c32.c b/networking/tls_sp_c32.c index 29dd04293..3b0473036 100644 --- a/networking/tls_sp_c32.c +++ b/networking/tls_sp_c32.c @@ -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.