diff --git a/tools/garaga_rs/src/bls12_381_final_exp_witness.rs b/tools/garaga_rs/src/bls12_381_final_exp_witness.rs
index 68353f19..35c081ed 100644
--- a/tools/garaga_rs/src/bls12_381_final_exp_witness.rs
+++ b/tools/garaga_rs/src/bls12_381_final_exp_witness.rs
@@ -1,5 +1,5 @@
 use ark_bls12_381::Fq12;
-use ark_ff::{Field, Zero};
+use ark_ff::Field;
 use num_bigint::BigInt;
 
 pub fn get_final_exp_witness(f: Fq12) -> (Fq12, Fq12) {
@@ -7,67 +7,64 @@ pub fn get_final_exp_witness(f: Fq12) -> (Fq12, Fq12) {
 }
 
 fn init() -> (BigInt, BigInt, BigInt) {
-    let x: BigInt = -BigInt::from(0xD201000000010000u64); // CURVES[CurveID.BLS12_381.value].x
+    let x = -BigInt::from(0xD201000000010000u64); // CURVES[CurveID.BLS12_381.value].x
     let k = 12;
-    let r: BigInt = x.pow(4) - x.pow(2) + 1;
-    let q: BigInt = (x.clone() - BigInt::from(1)).pow(2) / 3 * r.clone() + x.clone();
-    let h: BigInt = (q.pow(k) - 1) / r.clone();
+    let r = x.pow(4) - x.pow(2) + 1;
+    let q: BigInt = (&x - BigInt::from(1)).pow(2) / 3 * &r + &x;
+    let h = (q.pow(k) - 1) / &r;
 
-    let lam = -x + q.clone();
-    let m = lam.clone() / r;
+    let lam = -&x + &q;
+    let m = &lam / &r;
 
     let p = BigInt::from(5044125407647214251u64);
-    let h3 = h.clone() / (27 * p.clone());
+    let h3 = &h / (27 * &p);
 
     let e = lam.modinv(&h3).unwrap();
-    let s: BigInt = ((p.clone() * 27 - 1) * h3.modinv(&(p.clone() * 27)).unwrap()) % (p.clone() * 27);
+    let s = ((&p * 27 - 1) * h3.modinv(&(&p * 27)).unwrap()) % (&p * 27);
 
-    assert!(h % (27 * p.clone()) == BigInt::zero());
+    assert!(h % (27 * &p) == BigInt::from(0));
     assert!(m == 3 * p.pow(2));
 
-    assert!(gcd(BigInt::from(3), h3.clone()) == BigInt::from(1));
-    assert!(gcd(p.pow(2), h3.clone()) == BigInt::from(1));
-    assert!(gcd(p.clone(), h3.clone()) == BigInt::from(1));
-    assert!(gcd(p.clone(), 27 * h3.clone()) == BigInt::from(1));
-    assert!(gcd(BigInt::from(27), p * h3.clone()) == BigInt::from(1));
+    assert!(gcd(&BigInt::from(3), &h3) == BigInt::from(1));
+    assert!(gcd(&p.pow(2), &h3) == BigInt::from(1));
+    assert!(gcd(&p, &h3) == BigInt::from(1));
+    assert!(gcd(&p, &(27 * &h3)) == BigInt::from(1));
+    assert!(gcd(&BigInt::from(27), &(&p * &h3)) == BigInt::from(1));
 
-    assert!((q.pow(3) - 1) % 27 == BigInt::zero());
+    assert!((q.pow(3) - 1) % 27 == BigInt::from(0));
 
     return (h3, s, e);
 }
 
 fn get_root_and_scaling_factor_bls(mlo: Fq12) -> (Fq12, Fq12) {
-    let (h3, s, e) = init();
     /*
      * Takes a miller loop output and returns root, shift such that
      * root**lam = shift * mlo, if and only if mlo**h == 1.
      */
-    let x = mlo.pow(&bigint_to_u64ref_le(&h3));
-    let shift = x.pow(&bigint_to_u64ref_le(&s));
-    let root = (shift * mlo).pow(&bigint_to_u64ref_le(&e));
+    let (h3, s, e) = init();
+    let x = mlo.pow(&to_words_le(&h3));
+    let shift = x.pow(&to_words_le(&s));
+    let root = (shift * mlo).pow(&to_words_le(&e));
     return (root, shift);
 }
 
-fn gcd(a: BigInt, b: BigInt) -> BigInt {
-    let mut a = a;
-    let mut b = b;
-    while b != BigInt::zero() {
-        let temp = b.clone();
-        b = a % &b;
-        a = temp;
+fn gcd(a: &BigInt, b: &BigInt) -> BigInt {
+    let mut a = a.clone();
+    let mut b = b.clone();
+    while b != BigInt::from(0) {
+        (a, b) = (b.clone(), a % b);
     }
-    a
+    return a;
 }
 
-fn bigint_to_u64ref_le(bigint: &BigInt) -> Vec<u64> {
-    let bytes = bigint.to_bytes_le().1;
-    let num_words = (bytes.len() + 7) / 8;
-    let mut u64_words = Vec::with_capacity(num_words);
+fn to_words_le(bigint: &BigInt) -> Vec<u64> {
+    let (sign, bytes) = bigint.to_bytes_le();
+    assert!(sign != num_bigint::Sign::Minus);
+    let mut words = Vec::with_capacity((bytes.len() + 7) / 8);
     for chunk in bytes.chunks(8) {
         let mut word = [0u8; 8];
         word[..chunk.len()].copy_from_slice(chunk);
-        let u64_word = u64::from_le_bytes(word);
-        u64_words.push(u64_word);
+        words.push(u64::from_le_bytes(word));
     }
-    u64_words
+    return words;
 }