From af55a0ffaaffeaf95bf078977f2dd5c2d61c4068 Mon Sep 17 00:00:00 2001
From: avp <andres.valencia@csem.ch>
Date: Fri, 7 Jun 2024 16:19:18 +0200
Subject: [PATCH] Fix calculation of carry/borrow when right=0xFFFFFFFF and
 carry/borrow = 1

---
 uECC.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/uECC.c b/uECC.c
index a3d502c..9b5c78f 100644
--- a/uECC.c
+++ b/uECC.c
@@ -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;
@@ -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;