add hash of public params for Nova & HyperNova (#118)

- implement hash of public params for Nova & HyperNova
- abstract pp_hash computation for folding schemes
- add pp_hash to solidity contract generator to verify the decider proof

folding-schemes/src/folding/hypernova/lcccs.rs

@@ -10,7 +10,7 @@ use ark_std::rand::Rng;
 use ark_std::Zero;
 
 use super::Witness;
-use crate::ccs::CCS;
+use crate::arith::ccs::CCS;
 use crate::commitment::CommitmentScheme;
 use crate::folding::circuits::nonnative::affine::nonnative_affine_to_field_elements;
 use crate::utils::mle::dense_vec_to_dense_mle;
@@ -129,6 +129,7 @@ where
     pub fn hash(
         &self,
         poseidon_config: &PoseidonConfig<C::ScalarField>,
+        pp_hash: C::ScalarField,
         i: C::ScalarField,
         z_0: Vec<C::ScalarField>,
         z_i: Vec<C::ScalarField>,
@@ -138,7 +139,7 @@ where
         CRH::<C::ScalarField>::evaluate(
             poseidon_config,
             vec![
-                vec![i],
+                vec![pp_hash, i],
                 z_0,
                 z_i,
                 C_x,
@@ -164,9 +165,10 @@ pub mod tests {
     use std::sync::Arc;
 
     use super::*;
-    use crate::ccs::{
+    use crate::arith::{
+        ccs::tests::{get_test_ccs, get_test_z},
         r1cs::R1CS,
-        tests::{get_test_ccs, get_test_z},
+        Arith,
     };
     use crate::commitment::pedersen::Pedersen;
     use crate::utils::hypercube::BooleanHypercube;