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-rw-r--r--crypto/constant_time_locl.h18
1 files changed, 4 insertions, 14 deletions
diff --git a/crypto/constant_time_locl.h b/crypto/constant_time_locl.h
index c0483939fe3d..8af98c168329 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)));
}