diff options
Diffstat (limited to 'stack/smp/p_256_ecc_pp.cc')
| -rw-r--r-- | stack/smp/p_256_ecc_pp.cc | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/stack/smp/p_256_ecc_pp.cc b/stack/smp/p_256_ecc_pp.cc index b416e1d3f..911dc5498 100644 --- a/stack/smp/p_256_ecc_pp.cc +++ b/stack/smp/p_256_ecc_pp.cc @@ -245,3 +245,25 @@ void ECC_PointMult_Bin_NAF(Point* q, Point* p, uint32_t* n, multiprecision_mersenns_mult_mod(q->z, q->z, minus_p.x, keyLength); multiprecision_mersenns_mult_mod(q->y, q->y, q->z, keyLength); } + +bool ECC_ValidatePoint(const Point& pt) { + const size_t kl = KEY_LENGTH_DWORDS_P256; + p_256_init_curve(kl); + + // Ensure y^2 = x^3 + a*x + b (mod p); a = -3 + + // y^2 mod p + uint32_t y2_mod[kl] = {0}; + multiprecision_mersenns_squa_mod(y2_mod, (uint32_t*)pt.y, kl); + + // Right hand side calculation + uint32_t rhs[kl] = {0}; + multiprecision_mersenns_squa_mod(rhs, (uint32_t*)pt.x, kl); + uint32_t three[kl] = {0}; + three[0] = 3; + multiprecision_sub_mod(rhs, rhs, three, kl); + multiprecision_mersenns_mult_mod(rhs, rhs, (uint32_t*)pt.x, kl); + multiprecision_add_mod(rhs, rhs, curve_p256.b, kl); + + return multiprecision_compare(rhs, y2_mod, kl) == 0; +} |