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Update documentation and comments

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Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
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Gabor Mezei
2021-10-18 16:28:27 +02:00
parent 63bbba5c13
commit a316fc8eb0
2 changed files with 40 additions and 30 deletions
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6
library/constant_time.c
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@@ -228,14 +228,14 @@ int mbedtls_cf_cond_select_sign( unsigned char condition,
{
/* In order to avoid questions about what we can reasonnably assume about
* the representations of signed integers, move everything to unsigned
* by taking advantage of the fact that a and b are either +1 or -1. */
* by taking advantage of the fact that if1 and if0 are either +1 or -1. */
unsigned uif1 = if1 + 1;
unsigned uif0 = if0 + 1;
/* condition was 0 or 1, mask is 0 or 2 as are ua and ub */
/* condition was 0 or 1, mask is 0 or 2 as are uif1 and uif0 */
const unsigned mask = condition << 1;
/* select ua or ub */
/* select uif1 or uif0 */
unsigned ur = ( uif0 & ~mask ) | ( uif1 & mask );
/* ur is now 0 or 2, convert back to -1 or +1 */