93b886f54
Denys Vlasenko
2021-04-26
Subject
tls: shrink sp_256_mont_inv_10
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networking/tls_sp_c32.c+9 -1
| @@ -554,11 +554,18 @@ static void sp_256_mont_sqr_10(sp_digit* r, const sp_digit* a, const sp_digit* m | |
| * r Inverse result. | |
| * a Number to invert. | |
| */ | |
| + | #if 0 |
| /* Mod-2 for the P256 curve. */ | |
| static const uint32_t p256_mod_2[8] = { | |
| 0xfffffffd,0xffffffff,0xffffffff,0x00000000, | |
| 0x00000000,0x00000000,0x00000001,0xffffffff, | |
| }; | |
| + | //Bit pattern: |
| + | //2 2 2 2 2 2 2 1...1 |
| + | //5 5 4 3 2 1 0 9...0 9...1 |
| + | //543210987654321098765432109876543210987654321098765432109876543210...09876543210...09876543210 |
| + | //111111111111111111111111111111110000000000000000000000000000000100...00000111111...11111111101 |
| + | #endif |
| static void sp_256_mont_inv_10(sp_digit* r, sp_digit* a) | |
| { | |
| sp_digit t[2*10]; //can be just [10]? | |
| @@ -567,7 +574,8 @@ static void sp_256_mont_inv_10(sp_digit* r, sp_digit* a) | |
| memcpy(t, a, sizeof(sp_digit) * 10); | |
| for (i = 254; i >= 0; i--) { | |
| sp_256_mont_sqr_10(t, t, p256_mod, p256_mp_mod); | |
| - | if (p256_mod_2[i / 32] & ((sp_digit)1 << (i % 32))) |
| + | /*if (p256_mod_2[i / 32] & ((sp_digit)1 << (i % 32)))*/ |
| + | if (i >= 224 || i == 192 || (i <= 95 && i != 1)) |
| sp_256_mont_mul_10(t, t, a, p256_mod, p256_mp_mod); | |
| } | |
| memcpy(r, t, sizeof(sp_digit) * 10); | |