small polishing & rebase to latest main branch updates

folding-schemes/src/folding/nova/circuits.rs

@@ -183,12 +183,15 @@ where
         pp_hash: C::ScalarField, // public params hash
         U_i: &CI,
         u_i: &CI,
-        cmT: &C,
+        cmT: Option<&C>,
     ) -> Vec<bool> {
         transcript.absorb(&pp_hash);
         transcript.absorb(&U_i);
         transcript.absorb(&u_i);
-        transcript.absorb_nonnative(cmT);
+        // in the Nova case we absorb the cmT, in Ova case we don't since it is not used.
+        if let Some(cmT_value) = cmT {
+            transcript.absorb_nonnative(cmT_value);
+        }
         transcript.squeeze_bits(NOVA_N_BITS_RO)
     }
 
@@ -198,12 +201,15 @@ where
         pp_hash: FpVar<CF1<C>>,      // public params hash
         U_i_vec: Vec<FpVar<CF1<C>>>, // apready processed input, so we don't have to recompute these values
         u_i: CommittedInstanceVar<C>,
-        cmT: NonNativeAffineVar<C>,
+        cmT: Option<NonNativeAffineVar<C>>,
     ) -> Result<Vec<Boolean<C::ScalarField>>, SynthesisError> {
         transcript.absorb(&pp_hash)?;
         transcript.absorb(&U_i_vec)?;
         transcript.absorb(&u_i)?;
-        transcript.absorb_nonnative(&cmT)?;
+        // in the Nova case we absorb the cmT, in Ova case we don't since it is not used.
+        if let Some(cmT_value) = cmT {
+            transcript.absorb_nonnative(&cmT_value)?;
+        }
         transcript.squeeze_bits(NOVA_N_BITS_RO)
     }
 }
@@ -382,7 +388,7 @@ where
             pp_hash.clone(),
             U_i_vec,
             u_i.clone(),
-            cmT.clone(),
+            Some(cmT.clone()),
         )?;
         let r = Boolean::le_bits_to_fp_var(&r_bits)?;
         // Also convert r_bits to a `NonNativeFieldVar`
@@ -692,7 +698,7 @@ pub mod tests {
                 pp_hash,
                 &U_i,
                 &u_i,
-                &cmT,
+                Some(&cmT),
             );
         let r = Fr::from_bigint(BigInteger::from_bits_le(&r_bits)).unwrap();
 
@@ -721,7 +727,7 @@ pub mod tests {
                 pp_hashVar,
                 U_iVar_vec,
                 u_iVar,
-                cmTVar,
+                Some(cmTVar),
             )
             .unwrap();
         assert!(cs.is_satisfied().unwrap());

folding-schemes/src/folding/nova/decider.rs

@@ -13,7 +13,7 @@ use ark_std::{One, Zero};
 use core::marker::PhantomData;
 
 use super::decider_circuits::{DeciderCircuit1, DeciderCircuit2};
-use super::{nifs::NIFS, CommittedInstance, Nova};
+use super::{nifs::NIFS, traits::NIFSTrait, CommittedInstance, Nova};
 use crate::commitment::CommitmentScheme;
 use crate::folding::circuits::{
     cyclefold::CycleFoldCommittedInstance,

folding-schemes/src/folding/nova/decider_circuits.rs

@@ -288,7 +288,7 @@ where
             pp_hash,
             U_i_vec,
             u_i.clone(),
-            cmT.clone(),
+            Some(cmT.clone()),
         )?;
         // 5.1.
         let (incircuit_c_W, incircuit_c_E) =

folding-schemes/src/folding/nova/decider_eth_circuit.rs

@@ -260,7 +260,7 @@ where
             nova.pp_hash,
             &nova.U_i,
             &nova.u_i,
-            &cmT,
+            Some(&cmT),
         );
         let r_Fr = C1::ScalarField::from_bigint(BigInteger::from_bits_le(&r_bits))
             .ok_or(Error::OutOfBounds)?;
@@ -490,7 +490,7 @@ where
             pp_hash,
             U_i_vec,
             u_i.clone(),
-            cmT.clone(),
+            Some(cmT),
         )?;
         // 5.1.
         let (incircuit_c_W, incircuit_c_E) =

folding-schemes/src/folding/nova/mod.rs

@@ -689,7 +689,7 @@ where
             self.pp_hash,
             &self.U_i,
             &self.u_i,
-            &cmT,
+            Some(&cmT),
         );
         let r_Fr = C1::ScalarField::from_bigint(BigInteger::from_bits_le(&r_bits))
             .ok_or(Error::OutOfBounds)?;

folding-schemes/src/folding/nova/nifs.rs

@@ -98,10 +98,16 @@ where
         aux: &Self::VerifierAux, // cmT
     ) -> Vec<bool> {
         ChallengeGadget::<C, Self::CommittedInstance>::get_challenge_native(
-            transcript, pp_hash, U_i, u_i, aux,
+            transcript,
+            pp_hash,
+            U_i,
+            u_i,
+            Some(aux),
         )
     }
 
+    // Notice: `prove` method is implemented at the trait level.
+
     fn verify(
         // r comes from the transcript, and is a n-bit (N_BITS_CHALLENGE) element
         r: C::ScalarField,

folding-schemes/src/folding/nova/ova.rs

@@ -169,22 +169,20 @@ where
     ) -> Vec<bool> {
         // reuse Nova's get_challenge method
         ChallengeGadget::<C, Self::CommittedInstance>::get_challenge_native(
-            transcript,
-            pp_hash,
-            U_i,
-            u_i,
-            &C::zero(), // empty in Ova's case
+            transcript, pp_hash, U_i, u_i, None, // empty in Ova's case
         )
     }
 
+    // Notice: `prove` method is implemented at the trait level.
+
     fn verify(
         // r comes from the transcript, and is a n-bit (N_BITS_CHALLENGE) element
         r: C::ScalarField,
         U_i: &Self::CommittedInstance,
         u_i: &Self::CommittedInstance,
         _aux: &Self::VerifierAux,
     ) -> Self::CommittedInstance {
-        // recall that r <==> alpha, and u <==} mu between Nova and Ova respectively
+        // recall that r <==> alpha, and u <==> mu between Nova and Ova respectively
         let u = U_i.u + r; // u_i.u is always 1 IN ova as we just can do sequential IVC.
         let cmWE = U_i.cmWE + u_i.cmWE.mul(r);
         let x = U_i

folding-schemes/src/folding/nova/zk.rs

@@ -86,7 +86,11 @@ where
         cmT: C1,
     ) -> Result<C1::ScalarField, Error> {
         let r_bits = ChallengeGadget::<C1, CommittedInstance<C1>>::get_challenge_native(
-            sponge, pp_hash, &U_i, &u_i, &cmT,
+            sponge,
+            pp_hash,
+            &U_i,
+            &u_i,
+            Some(&cmT),
         );
         C1::ScalarField::from_bigint(BigInteger::from_bits_le(&r_bits)).ok_or(Error::OutOfBounds)
     }