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backend/src/stwo/prover.rs

@@ -576,7 +576,10 @@ fn get_dummy_challenges<MC: MerkleChannel>(
             })
         })
         .collect::<BTreeSet<_>>();
-
+    // Stwo provides a function to draw challenges from the secure field `QM31`,
+    // which consists of 4 `M31` elements. We calculate the total number of challenges
+    // needed in the `M31` field, round it up to the next multiple of 4,
+    // and then compute the number of draws required from the `QM31` field.
     let number_of_qm31_challenges = ((challenges_stage0.len() + 4) & !3) >> 2;
 
     let challenge_channel = &mut <MC as MerkleChannel>::C::default();
@@ -585,7 +588,7 @@ fn get_dummy_challenges<MC: MerkleChannel>(
         .flat_map(|_| {
             let qm31_challenge = challenge_channel.draw_felt();
             [
-                qm31_challenge.0.0,
+                qm31_challenge.0 .0,
                 qm31_challenge.0 .1,
                 qm31_challenge.1 .0,
                 qm31_challenge.1 .1,