diff options
Diffstat (limited to 'Cryptlib/OpenSSL/crypto/bn/bn_gf2m.c')
| -rw-r--r--[-rwxr-xr-x] | Cryptlib/OpenSSL/crypto/bn/bn_gf2m.c | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/Cryptlib/OpenSSL/crypto/bn/bn_gf2m.c b/Cryptlib/OpenSSL/crypto/bn/bn_gf2m.c index 5d90f1e8..28f1fa8f 100755..100644 --- a/Cryptlib/OpenSSL/crypto/bn/bn_gf2m.c +++ b/Cryptlib/OpenSSL/crypto/bn/bn_gf2m.c @@ -1095,3 +1095,54 @@ int BN_GF2m_arr2poly(const unsigned int p[], BIGNUM *a) return 1; } +/* + * Constant-time conditional swap of a and b. + * a and b are swapped if condition is not 0. The code assumes that at most one bit of condition is set. + * nwords is the number of words to swap. The code assumes that at least nwords are allocated in both a and b, + * and that no more than nwords are used by either a or b. + * a and b cannot be the same number + */ +void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords) + { + BN_ULONG t; + int i; + + bn_wcheck_size(a, nwords); + bn_wcheck_size(b, nwords); + + assert(a != b); + assert((condition & (condition - 1)) == 0); + assert(sizeof(BN_ULONG) >= sizeof(int)); + + condition = ((condition - 1) >> (BN_BITS2 - 1)) - 1; + + t = (a->top^b->top) & condition; + a->top ^= t; + b->top ^= t; + +#define BN_CONSTTIME_SWAP(ind) \ + do { \ + t = (a->d[ind] ^ b->d[ind]) & condition; \ + a->d[ind] ^= t; \ + b->d[ind] ^= t; \ + } while (0) + + + switch (nwords) { + default: + for (i = 10; i < nwords; i++) + BN_CONSTTIME_SWAP(i); + /* Fallthrough */ + case 10: BN_CONSTTIME_SWAP(9); /* Fallthrough */ + case 9: BN_CONSTTIME_SWAP(8); /* Fallthrough */ + case 8: BN_CONSTTIME_SWAP(7); /* Fallthrough */ + case 7: BN_CONSTTIME_SWAP(6); /* Fallthrough */ + case 6: BN_CONSTTIME_SWAP(5); /* Fallthrough */ + case 5: BN_CONSTTIME_SWAP(4); /* Fallthrough */ + case 4: BN_CONSTTIME_SWAP(3); /* Fallthrough */ + case 3: BN_CONSTTIME_SWAP(2); /* Fallthrough */ + case 2: BN_CONSTTIME_SWAP(1); /* Fallthrough */ + case 1: BN_CONSTTIME_SWAP(0); + } +#undef BN_CONSTTIME_SWAP +} |