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Bug calculation carry/borrow when right=0xFFFFFFFF and carry/borrow=1 #227

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Bug calculation carry/borrow when right=0xFFFFFFFF and carry/borrow=1 #227

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8 changes: 2 additions & 6 deletions uECC.c
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Original file line number Diff line number Diff line change
Expand Up @@ -340,9 +340,7 @@ uECC_VLI_API uECC_word_t uECC_vli_add(uECC_word_t *result,
wordcount_t i;
for (i = 0; i < num_words; ++i) {
uECC_word_t sum = left[i] + right[i] + carry;
if (sum != left[i]) {
carry = (sum < left[i]);
}
carry = ((sum-carry) < left[i]);
result[i] = sum;
}
return carry;
Expand All @@ -359,9 +357,7 @@ uECC_VLI_API uECC_word_t uECC_vli_sub(uECC_word_t *result,
wordcount_t i;
for (i = 0; i < num_words; ++i) {
uECC_word_t diff = left[i] - right[i] - borrow;
if (diff != left[i]) {
borrow = (diff > left[i]);
}
borrow = ( (diff+borrow) > left[i]);
result[i] = diff;
}
return borrow;
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