Refactor complement_254 function to handle sign correctly

iden3 · Aug 22, 2024 · b1f795d · b1f795d
1 parent 9a4215b
commit b1f795d
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/circom_algebra/src/modular_arithmetic.rs b/circom_algebra/src/modular_arithmetic.rs
@@ -95,6 +95,7 @@ pub fn multi_inv(values: &Vec<BigInt>, field: &BigInt) -> Vec<BigInt>{
 // 254 bit complement
 pub fn complement_254(elem: &BigInt, field: &BigInt) -> BigInt {
     let (sign, mut bit_repr) = bit_representation(elem);
+    let new_sign = if elem == &BigInt::from(0) { Sign::Plus } else { sign};
     while bit_repr.len() > 254 {
         bit_repr.pop();
     }
@@ -104,7 +105,7 @@ pub fn complement_254(elem: &BigInt, field: &BigInt) -> BigInt {
     for bit in &mut bit_repr {
         *bit = if *bit == 0 { 1 } else { 0 };
     }
-    let cp = BigInt::from_radix_le(sign, &bit_repr, 2).unwrap();
+    let cp = BigInt::from_radix_le(new_sign, &bit_repr, 2).unwrap();
     modulus(&cp, field)
 }