diff --git a/rsa/Makefile b/rsa/Makefile
index 1d3819d..80cf2bf 100644
--- a/rsa/Makefile
+++ b/rsa/Makefile
@@ -18,9 +18,15 @@ fast:
 profile:
 	gcc -Wall -Wextra -Werror -Wunused-function -pg $(SRC) -o $(NAME)
 
+profile-clang:
+	clang -Wall -Wextra -Werror -Wunused-function -pg $(SRC) -o $(NAME)
+
 profile-fast:
 	gcc -Wall -Wextra -Werror -Wunused-function -O3 -pg $(SRC) -o $(NAME)
 
+profile-fast-clang:
+	clang -Wall -Wextra -Werror -Wunused-function -O3 -pg $(SRC) -o $(NAME)
+
 fclean:
 	rm -rf $(NAME)
 
diff --git a/rsa/bigint.c b/rsa/bigint.c
index cfae50d..6d75a7d 100644
--- a/rsa/bigint.c
+++ b/rsa/bigint.c
@@ -68,29 +68,35 @@ int64_t bigint_cmp(bigint_t a, bigint_t b) {
 
 // TODO refactor/clean assume same length ?
 int bigint_dif(bigint_t a, bigint_t b) {
-	int cursor = a.len - 1;
-	while (cursor >= 0) {
+	int cursor = a.len;
+	while (--cursor >= 0) {
 		if (a.data[cursor] ^ b.data[cursor]) {
 			return 1;
 		}
-		cursor -= 1;
+		//cursor -= 1;
 	}
 
 	return 0;
 }
+
+void tool(bigint_t borrow, bigint_t *y, bigint_t zero, bigint_t a) {
+	while (bigint_dif(*y, zero)) {
+		for (size_t i = 0; i < a.len; i++) {
+			borrow.data[i] = ~a.data[i] & y->data[i];
+			a.data[i] = a.data[i] ^ y->data[i];
+		}
+		bigint_destroy(*y);
+		*y = assignable_bigint_bitwise_left_shift(borrow);
+	}
+
+}
+
 // TODO check opti
 void bigint_substraction(bigint_t a, bigint_t b) {
 	bigint_t borrow = bigint_clone(b);
 	bigint_t y = bigint_clone(b);
 	bigint_t zero = bigint_zero(a.len);
-	while (bigint_dif(borrow, zero)) {
-		for (size_t i = 0; i < a.len; i++) {
-			borrow.data[i] = ~a.data[i] & y.data[i];
-			a.data[i] = a.data[i] ^ y.data[i];
-		}
-		bigint_destroy(y);
-		y = assignable_bigint_bitwise_left_shift(borrow);
-	}
+	tool(borrow, &y, zero, a);
 	bigint_destroy(y);
 	bigint_destroy(borrow);
 	bigint_destroy(zero);