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Adjust fixed-time arithmetic to not use boolean ops

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Signed-off-by: Kevin Bracey <[email protected]>
This commit is contained in:
Kevin Bracey
2020-10-12 18:09:04 +03:00
parent 99c64e142e
commit 045e576e02
1 changed files with 3 additions and 3 deletions
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tinycrypt/ecc.c
+3 -3
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@@ -493,7 +493,7 @@ uECC_word_t uECC_vli_equal(const uECC_word_t *left, const uECC_word_t *right)
uECC_word_t cond_set(uECC_word_t p_true, uECC_word_t p_false, unsigned int cond)
{
return (p_true*(cond)) | (p_false*(!cond));
return (p_true*(cond)) | (p_false*(cond ^ 1));
}
/* Computes result = left - right, returning borrow, in constant time.
@@ -768,9 +768,9 @@ static uECC_word_t uECC_vli_add(uECC_word_t *result, const uECC_word_t *left,
cmpresult_t uECC_vli_cmp(const uECC_word_t *left, const uECC_word_t *right)
{
uECC_word_t tmp[NUM_ECC_WORDS];
uECC_word_t neg = !!uECC_vli_sub(tmp, left, right);
uECC_word_t neg = uECC_vli_sub(tmp, left, right);
uECC_word_t equal = uECC_vli_isZero(tmp);
return (!equal - 2 * neg);
return ((equal ^ 1) - 2 * neg);
}
/* Computes vli = vli >> 1. */