Commit c71d2c9d by Niels Möller

### Fixed miscomputation bugs in secp-256r1 modulo functions.

parent 549f95f8
 2015-12-10 Niels Möller * ecc-256.c (ecc_256_modp): Fixed carry propagation bug. Problem reported by Hanno Böck. (ecc_256_modq): Fixed another carry propagation bug. 2015-11-23 Niels Möller 2015-11-23 Niels Möller * nettle.texinfo: Document rsa_encrypt, rsa_decrypt and * nettle.texinfo: Document rsa_encrypt, rsa_decrypt and ... ...
 ... @@ -113,8 +113,19 @@ ecc_256_modp (const struct ecc_modulo *p, mp_limb_t *rp) ... @@ -113,8 +113,19 @@ ecc_256_modp (const struct ecc_modulo *p, mp_limb_t *rp) assert (q2 < 2); assert (q2 < 2); /* We multiply by two low limbs of p, 2^96 - 1, so we could use /* shifts rather than mul. */ n-1 n-2 n-3 n-4 +---+---+---+---+ | u1| u0| u low | +---+---+---+---+ - | q1(2^96-1)| +-------+---+ |q2(2^.)| +-------+ We multiply by two low limbs of p, 2^96 - 1, so we could use shifts rather than mul. */ t = mpn_submul_1 (rp + n - 4, p->m, 2, q1); t = mpn_submul_1 (rp + n - 4, p->m, 2, q1); t += cnd_sub_n (q2, rp + n - 3, p->m, 1); t += cnd_sub_n (q2, rp + n - 3, p->m, 1); t += (-q2) & 0xffffffff; t += (-q2) & 0xffffffff; ... @@ -124,7 +135,10 @@ ecc_256_modp (const struct ecc_modulo *p, mp_limb_t *rp) ... @@ -124,7 +135,10 @@ ecc_256_modp (const struct ecc_modulo *p, mp_limb_t *rp) u0 -= t; u0 -= t; t = (u1 < cy); t = (u1 < cy); u1 -= cy; u1 -= cy; u1 += cnd_add_n (t, rp + n - 4, p->m, 3); cy = cnd_add_n (t, rp + n - 4, p->m, 2); u0 += cy; u1 += (u0 < cy); u1 -= (-t) & 0xffffffff; u1 -= (-t) & 0xffffffff; } } rp[2] = u0; rp[2] = u0; ... @@ -211,7 +225,7 @@ ecc_256_modq (const struct ecc_modulo *q, mp_limb_t *rp) ... @@ -211,7 +225,7 @@ ecc_256_modq (const struct ecc_modulo *q, mp_limb_t *rp) /* Conditional add of p */ /* Conditional add of p */ u1 += t; u1 += t; u2 += (t<<32) + (u0 < t); u2 += (t<<32) + (u1 < t); t = cnd_add_n (t, rp + n - 4, q->m, 2); t = cnd_add_n (t, rp + n - 4, q->m, 2); u1 += t; u1 += t; ... ...
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