add cyclic and tree recursion and refactor

codex-plonky2-circuits/src/circuits/params.rs

@@ -8,7 +8,7 @@ use plonky2_poseidon2::poseidon2_hash::poseidon2::Poseidon2Hash;
 // hash function used. this is hackish way of doing it because
 // H::Hash is not consistent with HashOut<F> and causing a lot of headache
 // will look into this later.
-pub type HF = Poseidon2Hash;
+pub type HF = PoseidonHash;
 
 /// params used for the circuits
 /// should be defined prior to building the circuit

codex-plonky2-circuits/src/recursion/cyclic_recursion.rs

@@ -0,0 +1,249 @@
+use hashbrown::HashMap;
+use plonky2::hash::hash_types::{HashOut, HashOutTarget, RichField};
+use plonky2::iop::target::{BoolTarget, Target};
+use plonky2::iop::witness::{PartialWitness, WitnessWrite};
+use plonky2::plonk::circuit_builder::CircuitBuilder;
+use plonky2::plonk::circuit_data::{CircuitConfig, CircuitData, CommonCircuitData, VerifierCircuitData, VerifierCircuitTarget};
+use plonky2::plonk::config::{AlgebraicHasher, GenericConfig};
+use plonky2::plonk::proof::{ProofWithPublicInputs, ProofWithPublicInputsTarget};
+use plonky2::recursion::dummy_circuit::cyclic_base_proof;
+use plonky2_field::extension::Extendable;
+use plonky2_poseidon2::poseidon2_hash::poseidon2::Poseidon2;
+use crate::recursion::params::{F,D,C,Plonky2Proof,H};
+use crate::recursion::inner_circuit::InnerCircuit;
+use anyhow::Result;
+use plonky2::gates::noop::NoopGate;
+use plonky2::recursion::cyclic_recursion::check_cyclic_proof_verifier_data;
+use crate::circuits::utils::select_hash;
+
+/// cyclic circuit struct
+/// contains necessary data
+/// note: only keeps track of latest proof not all proofs.
+pub struct CyclicCircuit<
+    I: InnerCircuit,
+>{
+    pub layer: usize,
+    pub circ: I,
+    pub cyclic_target: Option<CyclicCircuitTargets<I>>,
+    pub cyclic_circuit_data: Option<CircuitData<F, C, D>>,
+    pub common_data: Option<CommonCircuitData<F, D>>,
+    pub latest_proof: Option<ProofWithPublicInputs<F, C, D>>,
+}
+
+/// targets need to be assigned for the cyclic circuit
+#[derive(Clone)]
+pub struct CyclicCircuitTargets<
+    I: InnerCircuit,
+>{
+    pub inner_targets: I::Targets,
+    pub condition: BoolTarget,
+    pub inner_cyclic_proof_with_pis: ProofWithPublicInputsTarget<D>,
+    pub verifier_data: VerifierCircuitTarget,
+}
+
+impl<
+    I: InnerCircuit,
+> CyclicCircuit<I> {
+
+    /// create a new cyclic circuit
+    pub fn new(circ: I) -> Self{
+        Self{
+            layer: 0,
+            circ,
+            cyclic_target: None,
+            cyclic_circuit_data: None,
+            common_data: None,
+            latest_proof: None,
+        }
+    }
+
+    /// builds the cyclic recursion circuit using any inner circuit I
+    /// returns the circuit data
+    pub fn build_circuit(
+        &mut self,
+    ) -> Result<()>{
+        // if the circuit data is already build then no need to rebuild
+        if self.cyclic_circuit_data.is_some(){
+            return Ok(());
+        }
+
+        // builder with standard recursion config
+        let config = CircuitConfig::standard_recursion_config();
+        let mut builder = CircuitBuilder::<F, D>::new(config);
+
+        //build the inner circuit
+        let inner_t = self.circ.build(& mut builder)?;
+
+        // common data for recursion
+        let mut common_data = common_data_for_recursion();
+        // the hash of the public input
+        let pub_input_hash = builder.add_virtual_hash_public_input();
+        // verifier data for inner proofs
+        let verifier_data_target = builder.add_verifier_data_public_inputs();
+        // common data should have same num of public input as inner proofs
+        common_data.num_public_inputs = builder.num_public_inputs();
+
+        // condition
+        let condition = builder.add_virtual_bool_target_safe();
+
+        // inner proof with public input
+        let inner_cyclic_proof_with_pis = builder.add_virtual_proof_with_pis(&common_data);
+        // get the hash of the pub input
+        let inner_cyclic_pis = &inner_cyclic_proof_with_pis.public_inputs;
+        let inner_pub_input_hash = HashOutTarget::try_from(&inner_cyclic_pis[0..4]).unwrap();
+        // now hash the current public input
+        let outer_pis = I::get_pub_input_targets(&inner_t)?;
+        let outer_pi_hash = builder.hash_n_to_hash_no_pad::<H>(outer_pis);
+        let zero_hash = HashOutTarget::from_vec([builder.zero(); 4].to_vec());
+        // if leaf pad with zeros
+        let inner_pi_hash_or_zero_hash = select_hash(&mut builder, condition, inner_pub_input_hash, zero_hash);
+        // hash current public input with previous hash
+        let mut hash_input = vec![];
+        hash_input.extend_from_slice(&outer_pi_hash.elements);
+        hash_input.extend_from_slice(&inner_pi_hash_or_zero_hash.elements);
+        let outer_pi_hash = builder.hash_n_to_hash_no_pad::<H>(hash_input);
+        // connect this up one to `pub_input_hash`
+        builder.connect_hashes(pub_input_hash,outer_pi_hash);
+
+        // connect entropy?
+
+        // verify proof in-circuit
+        builder.conditionally_verify_cyclic_proof_or_dummy::<C>(
+            condition,
+            &inner_cyclic_proof_with_pis,
+            &common_data,
+        )?;
+
+        // build the cyclic circuit
+        let cyclic_circuit_data = builder.build::<C>();
+
+        // assign targets
+        let cyc_t = CyclicCircuitTargets::<I>{
+            inner_targets: inner_t,
+            condition,
+            inner_cyclic_proof_with_pis,
+            verifier_data: verifier_data_target
+        };
+        // assign the data
+        self.cyclic_circuit_data = Some(cyclic_circuit_data);
+        self.common_data = Some(common_data);
+        self.cyclic_target = Some(cyc_t);
+        Ok(())
+    }
+
+    /// generates a proof with only one recursion layer
+    /// takes circuit input
+    pub fn prove_one_layer(
+        &mut self,
+        circ_input: &I::Input,
+    ) -> Result<ProofWithPublicInputs<F, C, D>>{
+
+        if self.cyclic_circuit_data.is_none(){
+            panic!("circuit data not found") // TODO: replace with err
+        }
+
+        let circ_data = self.cyclic_circuit_data.as_ref().unwrap();
+        let cyc_targets = self.cyclic_target.as_ref().unwrap();
+        let common_data = self.common_data.as_ref().unwrap();
+
+        // assign targets
+        let mut pw = PartialWitness::new();
+        self.circ.assign_targets(&mut pw,&cyc_targets.inner_targets,&circ_input)?;
+
+        // if leaf add dummy proof
+        if(self.layer == 0) {
+            pw.set_bool_target(cyc_targets.condition, false)?;
+            pw.set_proof_with_pis_target::<C, D>(
+                &cyc_targets.inner_cyclic_proof_with_pis,
+                &cyclic_base_proof(
+                    common_data,
+                    &circ_data.verifier_only,
+                    HashMap::new(),
+                ),
+            )?;
+        }else{ // else add last proof
+            pw.set_bool_target(cyc_targets.condition, true)?;
+            let last_proof = self.latest_proof.as_ref().unwrap();
+            pw.set_proof_with_pis_target(&cyc_targets.inner_cyclic_proof_with_pis, last_proof)?;
+        }
+
+        // assign verifier data
+        pw.set_verifier_data_target(&cyc_targets.verifier_data, &circ_data.verifier_only)?;
+        // prove
+        let proof = circ_data.prove(pw)?;
+        // check that the correct verifier data is consistent
+        check_cyclic_proof_verifier_data(
+            &proof,
+            &circ_data.verifier_only,
+            &circ_data.common,
+        )?;
+
+        self.latest_proof = Some(proof.clone());
+        self.layer = self.layer + 1;
+        Ok(proof)
+    }
+
+    /// prove n recursive layers
+    /// the function takes
+    /// - n: the number of layers and
+    /// - circ_input:  vector of n inputs
+    pub fn prove_n_layers(
+        &mut self,
+        n: usize,
+        circ_input: Vec<I::Input>,
+    ) -> Result<ProofWithPublicInputs<F, C, D>>{
+
+        // asserts that n equals the number of input
+        assert_eq!(n, circ_input.len());
+
+        for i in 0..n {
+            self.prove_one_layer(&circ_input[i])?;
+        }
+
+        Ok(self.latest_proof.clone().unwrap())
+    }
+
+    /// verifies the latest proof generated
+    pub fn verify_latest_proof(
+        &mut self,
+    ) -> Result<()>{
+        if(self.cyclic_circuit_data.is_none() || self.latest_proof.is_none()){
+            panic!("no circuit data or proof found");
+        }
+        let circ_data = self.cyclic_circuit_data.as_ref().unwrap();
+        let proof = self.latest_proof.clone().unwrap();
+
+        circ_data.verify(proof)?;
+
+        Ok(())
+    }
+}
+
+/// Generates `CommonCircuitData` usable for recursion.
+pub fn common_data_for_recursion() -> CommonCircuitData<F, D>
+{
+    // layer 1
+    let config = CircuitConfig::standard_recursion_config();
+    let builder = CircuitBuilder::<F, D>::new(config);
+    let data = builder.build::<C>();
+    // layer 2
+    let config = CircuitConfig::standard_recursion_config();
+    let mut builder = CircuitBuilder::<F, D>::new(config);
+    let proof = builder.add_virtual_proof_with_pis(&data.common);
+    let verifier_data =
+        builder.add_virtual_verifier_data(data.common.config.fri_config.cap_height);
+    builder.verify_proof::<C>(&proof, &verifier_data, &data.common);
+    let data = builder.build::<C>();
+    // layer 3
+    let config = CircuitConfig::standard_recursion_config();
+    let mut builder = CircuitBuilder::<F, D>::new(config);
+    let proof = builder.add_virtual_proof_with_pis(&data.common);
+    let verifier_data =
+        builder.add_virtual_verifier_data(data.common.config.fri_config.cap_height);
+    builder.verify_proof::<C>(&proof, &verifier_data, &data.common);
+    // pad with noop gates
+    while builder.num_gates() < 1 << 12 {
+        builder.add_gate(NoopGate, vec![]);
+    }
+    builder.build::<C>().common
+}

codex-plonky2-circuits/src/recursion/inner_circuit.rs

@@ -1,4 +1,4 @@
-use plonky2::iop::target::BoolTarget;
+use plonky2::iop::target::{BoolTarget, Target};
 use plonky2::iop::witness::PartialWitness;
 use plonky2::plonk::circuit_builder::CircuitBuilder;
 use crate::recursion::params::{F,C,D};
@@ -13,13 +13,21 @@ pub trait InnerCircuit<
 
     /// build the circuit logic and return targets to be assigned later
     fn build(
+        &self,
         builder: &mut CircuitBuilder<F, D>,
     ) -> anyhow::Result<Self::Targets>;
 
     /// assign the actual witness values for the current instance of the circuit.
     fn assign_targets(
+        &self,
         pw: &mut PartialWitness<F>,
         targets: &Self::Targets,
         input: &Self::Input,
     ) -> anyhow::Result<()>;
+
+    /// from the set of the targets, return only the targets which are public
+    /// TODO: this can probably be replaced with enum for Public/Private targets
+    fn get_pub_input_targets(
+        targets: &Self::Targets,
+    ) -> anyhow::Result<(Vec<Target>)>;
 }

codex-plonky2-circuits/src/recursion/mod.rs

@@ -1,8 +1,8 @@
-pub mod structs;
+pub mod inner_circuit;
-pub mod traits;
 pub mod simple_recursion;
 pub mod simple_recursion2;
 pub mod tree_recursion;
 pub mod params;
-pub mod sampling;
+pub mod sampling_inner_circuit;
+pub mod cyclic_recursion;
 

codex-plonky2-circuits/src/recursion/params.rs

@@ -1,11 +1,15 @@
+use plonky2::hash::poseidon::PoseidonHash;
+use plonky2::plonk::config::PoseidonGoldilocksConfig;
 use plonky2::plonk::proof::ProofWithPublicInputs;
 use plonky2_field::goldilocks_field::GoldilocksField;
 use plonky2_poseidon2::config::Poseidon2GoldilocksConfig;
 
 // recursion param
+// TODO: make it more generic or use global params
 pub type F = GoldilocksField;
 pub const D: usize = 2;
-pub type C = Poseidon2GoldilocksConfig;
+pub type C = PoseidonGoldilocksConfig;
+pub type H = PoseidonHash;
 pub type Plonky2Proof = ProofWithPublicInputs<F, C, D>;
 
 

codex-plonky2-circuits/src/recursion/sampling.rs

@@ -1,28 +0,0 @@
-use plonky2::iop::target::BoolTarget;
-use plonky2::iop::witness::PartialWitness;
-use plonky2::plonk::circuit_builder::CircuitBuilder;
-use crate::circuits::params::CircuitParams;
-use crate::circuits::sample_cells::{SampleCircuit, SampleCircuitInput, SampleTargets};
-use crate::recursion::params::{D, F};
-use crate::recursion::traits::InnerCircuit;
-
-pub struct SamplingRecursion {}
-
-impl InnerCircuit for SamplingRecursion{
-    type Targets = SampleTargets;
-    type Input = SampleCircuitInput<F, D>;
-
-    /// build the circuit
-    /// TODO: this build the circuit with default circuit params -> make it generic
-    fn build(builder: &mut CircuitBuilder<F, D>) -> anyhow::Result<Self::Targets> {
-        let circ = SampleCircuit::new(CircuitParams::default());
-        Ok(circ.sample_slot_circuit(builder))
-    }
-
-    fn assign_targets(pw: &mut PartialWitness<F>, targets: &Self::Targets, input: &Self::Input) -> anyhow::Result<()> {
-        let circ = SampleCircuit::<F,D>::new(CircuitParams::default());
-        // circ.sample_slot_assign_witness(pw,targets,input);
-        todo!()
-        // Ok(())
-    }
-}

codex-plonky2-circuits/src/recursion/sampling_inner_circuit.rs

@@ -0,0 +1,48 @@
+use plonky2::iop::target::{BoolTarget, Target};
+use plonky2::iop::witness::PartialWitness;
+use plonky2::plonk::circuit_builder::CircuitBuilder;
+use crate::circuits::params::CircuitParams;
+use crate::circuits::sample_cells::{SampleCircuit, SampleCircuitInput, SampleTargets};
+use crate::recursion::params::{D, F};
+use crate::recursion::inner_circuit::InnerCircuit;
+use crate::circuits::params;
+
+/// recursion Inner circuit for the sampling circuit
+#[derive(Clone, Debug)]
+pub struct SamplingRecursion {
+    pub sampling_circ: SampleCircuit<F,D>,
+}
+
+impl Default for SamplingRecursion {
+    fn default() -> Self {
+        Self{
+            sampling_circ: SampleCircuit::new(CircuitParams::default())
+        }
+    }
+}
+
+
+impl InnerCircuit for SamplingRecursion{
+    type Targets = SampleTargets;
+    type Input = SampleCircuitInput<F, D>;
+
+    /// build the circuit
+    fn build(&self, builder: &mut CircuitBuilder<F, D>) -> anyhow::Result<Self::Targets> {
+        Ok(self.sampling_circ.sample_slot_circuit(builder))
+    }
+
+    fn assign_targets(&self, pw: &mut PartialWitness<F>, targets: &Self::Targets, input: &Self::Input) -> anyhow::Result<()> {
+        Ok(self.sampling_circ.sample_slot_assign_witness(pw, targets, input))
+    }
+
+    /// returns the public input specific for this circuit which are:
+    /// `[slot_index, dataset_root, entropy]`
+    fn get_pub_input_targets(targets: &Self::Targets) -> anyhow::Result<(Vec<Target>)> {
+        let mut pub_targets = vec![];
+        pub_targets.push(targets.slot_index.clone());
+        pub_targets.extend_from_slice(&targets.dataset_root.elements);
+        pub_targets.extend_from_slice(&targets.entropy.elements);
+
+        Ok(pub_targets)
+    }
+}

codex-plonky2-circuits/src/recursion/simple_recursion.rs

@@ -1,3 +1,6 @@
+// this file is mainly draft implementation and experimentation of multiple simple approaches
+// NOTE: will be deleted later on ...
+
 use plonky2::hash::hash_types::{HashOut, HashOutTarget, RichField};
 use plonky2::iop::target::Target;
 use plonky2::iop::witness::{PartialWitness, WitnessWrite};

codex-plonky2-circuits/src/recursion/simple_recursion2.rs

@@ -1,3 +1,6 @@
+// this is still simple recursion approach but written differently,
+// still needs to be improved/removed.
+
 use plonky2::hash::hash_types::{HashOut, HashOutTarget, RichField};
 use plonky2::iop::witness::{PartialWitness, WitnessWrite};
 use plonky2::plonk::circuit_builder::CircuitBuilder;

codex-plonky2-circuits/src/recursion/tree_recursion.rs

@@ -1,69 +1,368 @@
+
 use hashbrown::HashMap;
 use plonky2::hash::hash_types::{HashOut, HashOutTarget, RichField};
-use plonky2::iop::target::Target;
+use plonky2::iop::target::{BoolTarget, Target};
 use plonky2::iop::witness::{PartialWitness, WitnessWrite};
 use plonky2::plonk::circuit_builder::CircuitBuilder;
-use plonky2::plonk::circuit_data::{CircuitData, VerifierCircuitData, VerifierCircuitTarget};
+use plonky2::plonk::circuit_data::{CircuitConfig, CircuitData, CommonCircuitData, VerifierCircuitData, VerifierCircuitTarget};
 use plonky2::plonk::config::{AlgebraicHasher, GenericConfig};
 use plonky2::plonk::proof::{ProofWithPublicInputs, ProofWithPublicInputsTarget};
 use plonky2::recursion::dummy_circuit::cyclic_base_proof;
 use plonky2_field::extension::Extendable;
 use plonky2_poseidon2::poseidon2_hash::poseidon2::Poseidon2;
 use crate::recursion::params::RecursionTreeParams;
-use crate::recursion::params::{F,D,C,Plonky2Proof};
+use crate::recursion::params::{F,D,C,Plonky2Proof,H};
-use crate::recursion::traits::InnerCircuit;
+use crate::recursion::inner_circuit::InnerCircuit;
+use anyhow::{anyhow, Result};
+use plonky2::gates::noop::NoopGate;
+use plonky2::recursion::cyclic_recursion::check_cyclic_proof_verifier_data;
+use crate::circuits::utils::select_hash;
 
-pub struct RecursionCircuit<
+/// the tree recursion struct simplifies the process
+/// of building, proving and verifying
+/// the two consts are:
+/// - M: number of inner circuits to run
+/// - N: number of inner proofs to verify
+pub struct TreeRecursion<
     I: InnerCircuit,
+    const M: usize,
+    const N: usize,
 >{
-    pub recursion_tree_params: RecursionTreeParams,
+    node_circ: NodeCircuit<I, M, N>
-    pub inner_circuit_targets: Vec<I::Targets>,
-    pub proof_targets: Vec<ProofWithPublicInputsTarget<D>>,
-    pub verifier_data_targets: VerifierCircuitTarget,
-    pub verifier_data: VerifierCircuitData<F, C, D>,
-    pub condition_targets: Vec<Target>,
-}
-
-pub struct RecursionCircuitInput<
-    I: InnerCircuit,
->{
-    pub inner_circuit_input: Vec<I::Targets>,
-    pub proofs: Plonky2Proof,
-    pub conditions: Vec<F>
 }
 
 impl<
     I: InnerCircuit,
-> RecursionCircuit<I> {
+    const M: usize,
+    const N: usize,
+> TreeRecursion<I, M, N> {
 
-    pub fn build_circuit(
+    pub fn new(node_circ: NodeCircuit<I,M,N>) -> Self{
+        Self{
+            node_circ,
+        }
+    }
+
+    pub fn build(
+        &mut self
+    ) -> Result<()>{
+        self.node_circ.build_circuit()
+    }
+
+    /// generates a proof - only one node
+    /// takes M circuit input and N proofs
+    pub fn prove(
+        &mut self,
+        circ_input: &[I::Input; M],
+        proofs_option: Option<[ProofWithPublicInputs<F, C, D>; N]>,
+        is_leaf: bool,
+    ) -> Result<ProofWithPublicInputs<F, C, D>>{
+
+        if self.node_circ.cyclic_circuit_data.is_none(){
+            panic!("circuit data not found") // TODO: replace with err
+        }
+
+        let mut pw = PartialWitness::new();
+        self.node_circ.assign_targets(
+            circ_input,
+            proofs_option,
+            &mut pw,
+            is_leaf,
+        )?;
+
+        let circ_data = self.node_circ.cyclic_circuit_data.as_ref().unwrap();
+        let cyc_targets = self.node_circ.cyclic_target.as_ref().unwrap();
+
+        pw.set_verifier_data_target(&cyc_targets.verifier_data, &circ_data.verifier_only)?;
+        let proof = circ_data.prove(pw)?;
+        check_cyclic_proof_verifier_data(
+            &proof,
+            &circ_data.verifier_only,
+            &circ_data.common,
+        )?;
+
+        Ok(proof)
+    }
+
+    /// prove n in a tree structure recursively
+    /// the function takes
+    /// - circ_input:  vector of circuit inputs
+    pub fn prove_n_nodes(
+        &mut self,
+        circ_input: Vec<I::Input>,
+    ) -> Result<ProofWithPublicInputs<F, C, D>>{
+        todo!()
+    }
+
+    /// verifies the proof generated
+    pub fn verify_proof(
         &self,
-        builder: &mut CircuitBuilder::<F, D>,
+        proof: ProofWithPublicInputs<F, C, D>
-    ) -> Self {
+    ) -> Result<()>{
-        todo!()
+        if self.node_circ.cyclic_circuit_data.is_none() {
-    }
+            panic!("no circuit data or proof found");
-
+        }
-    pub fn get_circuit_data() -> CircuitData<F, C, D>{
+        let circ_data = self.node_circ.cyclic_circuit_data.as_ref().unwrap();
-        todo!()
+        circ_data.verify(proof)?;
-    }
-
-    pub fn get_dummy_proof(circuit_data: CircuitData<F, C, D>) -> Plonky2Proof {
-        let verifier_data = circuit_data.verifier_data();
-        let dummy_proof_with_pis = cyclic_base_proof(
-            &circuit_data.common,
-            &verifier_data.verifier_only,
-            HashMap::new(),
-        );
-        dummy_proof_with_pis
-    }
-
-    pub fn assign_witness(
-        &self,
-        pw: &mut PartialWitness<F>,
-        witnesses: RecursionCircuitInput<I>
-    )-> anyhow::Result<()>{
-        todo!()
-        // Ok(())
 
+        Ok(())
     }
 }
+
+
+/// Node circuit struct
+/// contains necessary data
+/// M: number of inner-circuits to run
+/// N: number of proofs verified in-circuit (so num of child nodes)
+pub struct NodeCircuit<
+    I: InnerCircuit,
+    const M: usize,
+    const N: usize,
+>{
+    pub circ: I,
+    pub cyclic_target: Option<NodeCircuitTargets<I,M,N>>,
+    pub cyclic_circuit_data: Option<CircuitData<F, C, D>>,
+    pub common_data: Option<CommonCircuitData<F, D>>,
+}
+
+/// Node circuit targets
+/// assumes that all inner proofs use the same verifier data
+#[derive(Clone, Debug)]
+pub struct NodeCircuitTargets<
+    I: InnerCircuit,
+    const M: usize,
+    const N: usize,
+>{
+    pub inner_targets: [I::Targets; M],
+    pub condition: BoolTarget,
+    pub inner_proofs_with_pis: [ProofWithPublicInputsTarget<D>; N],
+    pub verifier_data: VerifierCircuitTarget,
+}
+
+impl<
+    I: InnerCircuit,
+    const M: usize,
+    const N: usize,
+> NodeCircuit<I, M, N> {
+
+    /// create a new cyclic circuit
+    pub fn new(circ: I) -> Self{
+        Self{
+            circ,
+            cyclic_target: None,
+            cyclic_circuit_data: None,
+            common_data: None,
+        }
+    }
+
+    /// builds the cyclic recursion circuit using any inner circuit I
+    /// returns the circuit data
+    pub fn build_circuit(
+        &mut self,
+    ) -> Result<()>{
+        // if the circuit data is already build then no need to rebuild
+        if self.cyclic_circuit_data.is_some(){
+            return Ok(());
+        }
+
+        // builder with standard recursion config
+        let config = CircuitConfig::standard_recursion_config();
+        let mut builder = CircuitBuilder::<F, D>::new(config);
+
+        //build M inner circuits
+        // let mut inner_t = Vec::with_capacity(M);
+        // for i in 0..M {
+        //     inner_t.push( self.circ.build(&mut builder)?);
+        // }
+
+        let inner_t: [I::Targets; M] = (0..M)
+            .map(|_| self.circ.build(&mut builder))
+            .collect::<Result<Vec<_>>>()?
+            .try_into()
+            .map_err(|_| anyhow!("Expected exactly M inner circuits"))?;
+
+        // common data for recursion
+        let mut common_data = self.common_data_for_node()?;
+        // let outer_pis = I::get_pub_input_targets(&inner_t)?;
+        let pub_input_hash = builder.add_virtual_hash_public_input();
+        let verifier_data_target = builder.add_verifier_data_public_inputs();
+        common_data.num_public_inputs = builder.num_public_inputs();
+
+        // condition
+        let condition = builder.add_virtual_bool_target_safe();
+
+        // inner proofs targets - N proof targets
+        // let mut inner_cyclic_proof_with_pis = vec![];
+        // for i in 0..N {
+        //     inner_cyclic_proof_with_pis.push(builder.add_virtual_proof_with_pis(&common_data));
+        // }
+
+        let inner_cyclic_proof_with_pis: [ProofWithPublicInputsTarget<D>; N] = (0..N)
+            .map(|_| builder.add_virtual_proof_with_pis(&common_data))
+            .collect::<Vec<_>>()
+            .try_into()
+            .map_err(|_| anyhow!("Expected exactly N proof targets"))?;
+
+        // get the public input hash from all inner proof targets
+        let mut inner_pub_input_hashes = vec![];
+        for i in 0..N {
+            let inner_cyclic_pis = &inner_cyclic_proof_with_pis[i].public_inputs;
+            inner_pub_input_hashes.extend_from_slice(&inner_cyclic_pis[0..4]);
+        }
+        // hash all the inner public input h = H(h_1 | h_2 | ... | h_N)
+        let inner_pub_input_hash = builder.hash_n_to_hash_no_pad::<H>(inner_pub_input_hashes);
+
+        // get the public input of the inner circuit
+        let mut outer_pis = vec![];
+        for i in 0..M {
+            outer_pis.push( I::get_pub_input_targets(&inner_t[i])?);
+        }
+        // hash all the public input -> generate one hashout at the end
+        // this is not an optimal way to do it, verification might be ugly if M > 1
+        // TODO: optimize this
+        let mut outer_pi_hashes = vec![];
+        for i in 0..M {
+            let hash_res = builder.hash_n_to_hash_no_pad::<H>(outer_pis[i].clone());
+            outer_pi_hashes.extend_from_slice(&hash_res.elements)
+        }
+        // the final public input hash
+        let outer_pi_hash = builder.hash_n_to_hash_no_pad::<H>(outer_pi_hashes);
+        // zero hash for leaves
+        let zero_hash = HashOutTarget::from_vec([builder.zero(); 4].to_vec());
+        // if the inner proofs are dummy then use zero hash for public input
+        let inner_pi_hash_or_zero_hash = select_hash(&mut builder, condition, inner_pub_input_hash, zero_hash);
+
+        // now hash the public input of the inner proofs and outer proof so we have one public hash
+        let mut hash_input = vec![];
+        hash_input.extend_from_slice(&outer_pi_hash.elements);
+        hash_input.extend_from_slice(&inner_pi_hash_or_zero_hash.elements);
+        let outer_pi_hash = builder.hash_n_to_hash_no_pad::<H>(hash_input);
+        // connect this up one to `pub_input_hash`
+        builder.connect_hashes(pub_input_hash,outer_pi_hash);
+
+        // we can connect entropy, since all share same entropy, but might be more work
+        // TODO: look into entropy
+
+        // verify all N proofs in-circuit
+        for i in 0..N {
+            builder.conditionally_verify_cyclic_proof_or_dummy::<C>(
+                condition,
+                &inner_cyclic_proof_with_pis[i],
+                &common_data,
+            )?;
+        }
+
+        // build the cyclic circuit
+        let cyclic_circuit_data = builder.build::<C>();
+
+        // assign targets
+        let cyc_t = NodeCircuitTargets::<I, M, N>{
+            inner_targets: inner_t,
+            condition,
+            inner_proofs_with_pis: inner_cyclic_proof_with_pis,
+            verifier_data: verifier_data_target
+        };
+        // assign the data
+        self.cyclic_circuit_data = Some(cyclic_circuit_data);
+        self.common_data = Some(common_data);
+        self.cyclic_target = Some(cyc_t);
+        Ok(())
+    }
+
+    /// assigns the targets for the Node circuit
+    /// takes circuit input
+    pub fn assign_targets(
+        &mut self,
+        circ_input: &[I::Input; M],
+        proof_options: Option<[ProofWithPublicInputs<F, C, D>; N]>,
+        pw: &mut PartialWitness<F>,
+        is_leaf: bool,
+    ) -> Result<()>{
+
+        if self.cyclic_circuit_data.is_none(){
+            panic!("circuit data not found") // TODO: replace with err
+        }
+
+        let circ_data = self.cyclic_circuit_data.as_ref().unwrap();
+        let cyc_targets = self.cyclic_target.as_ref().unwrap();
+        let common_data = self.common_data.as_ref().unwrap();
+
+        for i in 0..M {
+            self.circ.assign_targets(pw, &cyc_targets.inner_targets[i], &circ_input[i])?;
+        }
+
+        if(is_leaf == true) {
+            pw.set_bool_target(cyc_targets.condition, false)?;
+            for i in 0..N {
+                pw.set_proof_with_pis_target::<C, D>(
+                    &cyc_targets.inner_proofs_with_pis[i],
+                    &cyclic_base_proof(
+                        common_data,
+                        &circ_data.verifier_only,
+                        HashMap::new(),
+                    ),
+                )?;
+            }
+        }else{
+            pw.set_bool_target(cyc_targets.condition, true)?;
+            let proofs = proof_options.unwrap(); // add error check
+            for i in 0..N {
+                pw.set_proof_with_pis_target(&cyc_targets.inner_proofs_with_pis[i], &proofs[i])?;
+            }
+        }
+
+        pw.set_verifier_data_target(&cyc_targets.verifier_data, &circ_data.verifier_only)?;
+
+        Ok(())
+    }
+
+    /// Generates `CommonCircuitData` usable for node recursion.
+    /// the circuit being built here depends on M and N so must be re-generated
+    /// if the params change
+    pub fn common_data_for_node(&self) -> Result<CommonCircuitData<F, D>>
+    {
+        // layer 1
+        let config = CircuitConfig::standard_recursion_config();
+        let builder = CircuitBuilder::<F, D>::new(config);
+        let data = builder.build::<C>();
+
+        // layer 2
+        let config = CircuitConfig::standard_recursion_config();
+        let mut builder = CircuitBuilder::<F, D>::new(config.clone());
+        let verifier_data = builder.add_virtual_verifier_data(data.common.config.fri_config.cap_height);
+        // generate and verify N number of proofs
+        for _ in 0..N {
+            let proof = builder.add_virtual_proof_with_pis(&data.common);
+            builder.verify_proof::<C>(&proof, &verifier_data, &data.common);
+        }
+        let data = builder.build::<C>();
+
+        // layer 3
+        let config = CircuitConfig::standard_recursion_config();
+        let mut builder = CircuitBuilder::<F, D>::new(config.clone());
+
+        // add a ConstantGate
+        builder.add_gate(
+            plonky2::gates::constant::ConstantGate::new(config.num_constants),
+            vec![],
+        );
+
+        // build M inner circuits
+        for i in 0..M {
+            self.circ.build(&mut builder)?;
+        }
+
+        // generate and verify N number of proofs
+        let verifier_data = builder.add_verifier_data_public_inputs();
+        for _ in 0..N {
+            let proof = builder.add_virtual_proof_with_pis(&data.common);
+            builder.verify_proof::<C>(&proof, &verifier_data, &data.common);
+        }
+        // pad. TODO: optimize this padding to only needed number of gates
+        while builder.num_gates() < 1 << 13 {
+            builder.add_gate(NoopGate, vec![]);
+        }
+        Ok(builder.build::<C>().common)
+    }
+
+}