diff options
Diffstat (limited to 'crypto/constant_time_locl.h')
| -rw-r--r-- | crypto/constant_time_locl.h | 18 |
1 files changed, 4 insertions, 14 deletions
diff --git a/crypto/constant_time_locl.h b/crypto/constant_time_locl.h index c048393..8af98c1 100644 --- a/crypto/constant_time_locl.h +++ b/crypto/constant_time_locl.h @@ -129,17 +129,12 @@ static inline int constant_time_select_int(unsigned int mask, int a, int b); static inline unsigned int constant_time_msb(unsigned int a) { - return (unsigned int)((int)(a) >> (sizeof(int) * 8 - 1)); + return 0-(a >> (sizeof(a) * 8 - 1)); } static inline unsigned int constant_time_lt(unsigned int a, unsigned int b) { - unsigned int lt; - /* Case 1: msb(a) == msb(b). a < b iff the MSB of a - b is set.*/ - lt = ~(a ^ b) & (a - b); - /* Case 2: msb(a) != msb(b). a < b iff the MSB of b is set. */ - lt |= ~a & b; - return constant_time_msb(lt); + return constant_time_msb(a^((a^b)|((a-b)^b))); } static inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b) @@ -149,12 +144,7 @@ static inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b) static inline unsigned int constant_time_ge(unsigned int a, unsigned int b) { - unsigned int ge; - /* Case 1: msb(a) == msb(b). a >= b iff the MSB of a - b is not set.*/ - ge = ~((a ^ b) | (a - b)); - /* Case 2: msb(a) != msb(b). a >= b iff the MSB of a is set. */ - ge |= a & ~b; - return constant_time_msb(ge); + return ~constant_time_lt(a, b); } static inline unsigned char constant_time_ge_8(unsigned int a, unsigned int b) @@ -204,7 +194,7 @@ static inline unsigned char constant_time_select_8(unsigned char mask, return (unsigned char)(constant_time_select(mask, a, b)); } -inline int constant_time_select_int(unsigned int mask, int a, int b) +static inline int constant_time_select_int(unsigned int mask, int a, int b) { return (int)(constant_time_select(mask, (unsigned)(a), (unsigned)(b))); } |