diff options
| -rw-r--r-- | networking/tls_sp_c32.c | 38 |
1 files changed, 24 insertions, 14 deletions
diff --git a/networking/tls_sp_c32.c b/networking/tls_sp_c32.c index 1ab6106..6fca2aa 100644 --- a/networking/tls_sp_c32.c +++ b/networking/tls_sp_c32.c @@ -569,8 +569,10 @@ static int sp_256_mul_add_8(sp_digit* r /*, const sp_digit* a, sp_digit b*/) // const sp_digit* a = p256_mod; //a[7..0] = ffffffff 00000001 00000000 00000000 00000000 ffffffff ffffffff ffffffff sp_digit b = r[0]; - uint64_t t = 0; + uint64_t t; + +// t = 0; // for (i = 0; i < 8; i++) { // uint32_t t_hi; // uint64_t m = ((uint64_t)b * a[i]) + r[i]; @@ -584,12 +586,13 @@ static int sp_256_mul_add_8(sp_digit* r /*, const sp_digit* a, sp_digit b*/) // Unroll, then optimize the above loop: //uint32_t t_hi; uint64_t m; + uint32_t t32; //m = ((uint64_t)b * a[0]) + r[0]; // Since b is r[0] and a[0] is ffffffff, the above optimizes to: // m = r[0] * ffffffff + r[0] = (r[0] * 100000000 - r[0]) + r[0] = r[0] << 32; //t += m; - // t = (uint64_t)r[0] << 32; + // t = r[0] << 32 = b << 32; //t_hi = (t < m); // t_hi = 0; //r[0] = (sp_digit)t; @@ -625,42 +628,49 @@ static int sp_256_mul_add_8(sp_digit* r /*, const sp_digit* a, sp_digit b*/) // Since a[3] is 00000000, the above optimizes to: // m = b * 0 + r[3] = r[3]; //t += m; - // t += r[3]; + // t = b + r[3]; //t_hi = (t < m); // t_hi = 0; //r[3] = (sp_digit)t; r[3] = r[3] + b; //t = (t >> 32) | ((uint64_t)t_hi << 32); - t = (r[3] < b); + t32 = (r[3] < b); // 0 or 1 //m = ((uint64_t)b * a[4]) + r[4]; // Since a[4] is 00000000, the above optimizes to: // m = b * 0 + r[4] = r[4]; //t += m; - t += r[4]; + // t = t32 + r[4]; //t_hi = (t < m); // t_hi = 0; - r[4] = (sp_digit)t; + //r[4] = (sp_digit)t; //t = (t >> 32) | ((uint64_t)t_hi << 32); - t = (t >> 32); + if (t32 != 0) { + r[4]++; + t32 = (r[4] == 0); // 0 or 1 //m = ((uint64_t)b * a[5]) + r[5]; // Since a[5] is 00000000, the above optimizes to: // m = b * 0 + r[5] = r[5]; //t += m; - t += r[5]; + // t = t32 + r[5]; (t32 is 0 or 1) //t_hi = (t < m); // t_hi = 0; - r[5] = (sp_digit)t; + //r[5] = (sp_digit)t; //t = (t >> 32) | ((uint64_t)t_hi << 32); - t = (t >> 32); + if (t32 != 0) { + r[5]++; + t32 = (r[5] == 0); // 0 or 1 + } + } //m = ((uint64_t)b * a[6]) + r[6]; // Since a[6] is 00000001, the above optimizes to: - m = (uint64_t)b + r[6]; // 33 bits at most - t += m; + // m = (uint64_t)b + r[6]; // 33 bits at most + //t += m; + t = t32 + (uint64_t)b + r[6]; //t_hi = (t < m); - // t_hi = 0; //32bit_value + 33bit_value can't overflow 64 bits + // t_hi = 0; r[6] = (sp_digit)t; //t = (t >> 32) | ((uint64_t)t_hi << 32); t = (t >> 32); @@ -671,7 +681,7 @@ static int sp_256_mul_add_8(sp_digit* r /*, const sp_digit* a, sp_digit b*/) m = ((uint64_t)b << 32) - b + r[7]; t += m; //t_hi = (t < m); - // t_hi in fact is always 0 here + // t_hi in fact is always 0 here (256bit * 32bit can't have more than 32 bits of overflow) r[7] = (sp_digit)t; //t = (t >> 32) | ((uint64_t)t_hi << 32); t = (t >> 32); |