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Feature/nova ivc (#36)
* Implement Nova IVC's new & prove_step methods Implement Nova IVC's new & prove_step methods (without CycleFold part yet) * transcript.absorb_point err handling, and update C.xy() usage * add transcript usage to IVC prove, add NovaTranscript trait extending Transcript trait, refactor NIFS.P to allow absorbing in transcript inbetween * Implement Nova's IVC.V method (without CycleFold part yet) * clippy lints * move challenge r computation in-circuit * reuse computed points with coordinates over CF (non-native) to save constraints in AugmentedFCircuit (constraint count went down ~6k) * rm 128 bit constant * add params to Errors * Updates from review suggestions. Additionally refactored nova/nifs fold, and rm transcript from nova/IVC. - Updates from PR suggestions - Additionally updated: - in nova/nifs.rs: reuse folded_committed_instance for verify_folded_instance, computationally is the same, but reusing the same code so avoiding duplication and having an error on one of the two versions. - in nova/ivc.rs: remove transcript from IVC (not needed, it uses the RO)main
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15 changed files with 663 additions and 174 deletions
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+1 -1rust-toolchain
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+3 -1src/constants.rs
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+2 -2src/decider/circuit.rs
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+18 -24src/folding/circuits/nonnative.rs
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+198 -68src/folding/nova/circuits.rs
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+261 -0src/folding/nova/ivc.rs
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+4 -16src/folding/nova/mod.rs
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+53 -24src/folding/nova/nifs.rs
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+67 -0src/folding/nova/traits.rs
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+14 -6src/lib.rs
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+10 -7src/pedersen.rs
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+2 -1src/transcript/mod.rs
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+25 -20src/transcript/poseidon.rs
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+1 -0src/utils/espresso/sum_check/prover.rs
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+4 -4src/utils/vec.rs
@ -1 +1 @@ |
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1.71.1 |
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1.73.0 |
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@ -1 +1,3 @@ |
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pub const N_BITS_CHALLENGE: usize = 250;
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// used for committed instances hash, so when going to the other curve of the cycle it does not
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// overflow the scalar field
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pub const N_BITS_HASH: usize = 250;
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@ -0,0 +1,261 @@ |
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use ark_crypto_primitives::sponge::{poseidon::PoseidonConfig, Absorb};
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use ark_ec::{CurveGroup, Group};
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use ark_ff::PrimeField;
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use ark_relations::r1cs::ConstraintSynthesizer;
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use ark_relations::r1cs::ConstraintSystem;
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use ark_std::rand::Rng;
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use ark_std::{One, Zero};
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use core::marker::PhantomData;
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use super::circuits::{AugmentedFCircuit, FCircuit};
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use super::{nifs::NIFS, traits::NovaR1CS, CommittedInstance, Witness};
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use crate::ccs::r1cs::R1CS;
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use crate::frontend::arkworks::{extract_r1cs, extract_z}; // TODO once Frontend trait is ready, use that
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use crate::pedersen::{Params as PedersenParams, Pedersen};
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use crate::Error;
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/// Implements the Incremental Verifiable Computation described in sections 1.2 and 5 of
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/// [Nova](https://eprint.iacr.org/2021/370.pdf)
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pub struct IVC<C1, C2, FC>
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where
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C1: CurveGroup,
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C2: CurveGroup,
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FC: FCircuit<C1::ScalarField>,
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{
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_c2: PhantomData<C2>,
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r1cs: R1CS<C1::ScalarField>,
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poseidon_config: PoseidonConfig<C1::ScalarField>,
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pedersen_params: PedersenParams<C1>,
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F: FC, // F circuit
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i: C1::ScalarField,
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z_0: Vec<C1::ScalarField>,
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z_i: Vec<C1::ScalarField>,
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w_i: Witness<C1>,
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u_i: CommittedInstance<C1>,
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W_i: Witness<C1>,
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U_i: CommittedInstance<C1>,
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}
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impl<C1, C2, FC> IVC<C1, C2, FC>
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where
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C1: CurveGroup,
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C2: CurveGroup,
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FC: FCircuit<C1::ScalarField>,
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<C1 as CurveGroup>::BaseField: PrimeField,
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<C1 as Group>::ScalarField: Absorb,
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{
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/// Initializes the IVC for the given parameters and initial state `z_0`.
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pub fn new<R: Rng>(
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rng: &mut R,
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poseidon_config: PoseidonConfig<C1::ScalarField>,
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F: FC,
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z_0: Vec<C1::ScalarField>,
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) -> Result<Self, Error> {
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// prepare the circuit to obtain its R1CS
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let cs = ConstraintSystem::<C1::ScalarField>::new_ref();
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let augmented_F_circuit = AugmentedFCircuit::<C1, FC>::empty(&poseidon_config, F);
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augmented_F_circuit.generate_constraints(cs.clone())?;
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cs.finalize();
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let cs = cs.into_inner().ok_or(Error::NoInnerConstraintSystem)?;
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let r1cs = extract_r1cs::<C1::ScalarField>(&cs);
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let pedersen_params = Pedersen::<C1>::new_params(rng, r1cs.A.n_rows);
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// setup the dummy instances
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let (w_dummy, u_dummy) = r1cs.dummy_instance();
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// W_i=W_0 is a 'dummy witness', all zeroes, but with the size corresponding to the R1CS that
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// we're working with.
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// Set U_i to be dummy instance
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Ok(Self {
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_c2: PhantomData,
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r1cs,
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poseidon_config,
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pedersen_params,
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F,
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i: C1::ScalarField::zero(),
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z_0: z_0.clone(),
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z_i: z_0,
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w_i: w_dummy.clone(),
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u_i: u_dummy.clone(),
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W_i: w_dummy,
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U_i: u_dummy,
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})
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}
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/// Implements IVC.P
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pub fn prove_step(&mut self) -> Result<(), Error> {
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let u_i1_x: C1::ScalarField;
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let augmented_F_circuit: AugmentedFCircuit<C1, FC>;
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let z_i1 = self.F.step_native(self.z_i.clone());
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let (W_i1, U_i1, cmT): (Witness<C1>, CommittedInstance<C1>, C1);
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if self.i == C1::ScalarField::zero() {
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// base case: i=0, z_i=z_0, U_i = U_d := dummy instance
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// u_1.x = H(1, z_0, z_i, U_i)
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u_i1_x = self.U_i.hash(
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&self.poseidon_config,
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C1::ScalarField::one(),
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self.z_0.clone(),
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z_i1.clone(),
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)?;
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(W_i1, U_i1, cmT) = (self.w_i.clone(), self.u_i.clone(), C1::generator());
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// base case
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augmented_F_circuit = AugmentedFCircuit::<C1, FC> {
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poseidon_config: self.poseidon_config.clone(),
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i: Some(C1::ScalarField::zero()), // = i=0
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z_0: Some(self.z_0.clone()), // = z_i
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z_i: Some(self.z_i.clone()),
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u_i: Some(self.u_i.clone()), // = dummy
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U_i: Some(self.U_i.clone()), // = dummy
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U_i1: Some(U_i1.clone()), // = dummy
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cmT: Some(cmT),
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F: self.F,
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x: Some(u_i1_x),
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};
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} else {
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let T: Vec<C1::ScalarField>;
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(T, cmT) = NIFS::<C1>::compute_cmT(
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&self.pedersen_params,
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&self.r1cs,
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&self.w_i,
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&self.u_i,
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&self.W_i,
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&self.U_i,
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)?;
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let r_Fr = AugmentedFCircuit::<C1, FC>::get_challenge_native(
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&self.poseidon_config,
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self.u_i.clone(),
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self.U_i.clone(),
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cmT,
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)?;
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// compute W_{i+1} and U_{i+1}
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(W_i1, U_i1) = NIFS::<C1>::fold_instances(
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r_Fr, &self.w_i, &self.u_i, &self.W_i, &self.U_i, &T, cmT,
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)?;
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self.r1cs.check_relaxed_instance_relation(&W_i1, &U_i1)?;
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// folded instance output (public input, x)
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// u_{i+1}.x = H(i+1, z_0, z_{i+1}, U_{i+1})
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u_i1_x = U_i1.hash(
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&self.poseidon_config,
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self.i + C1::ScalarField::one(),
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self.z_0.clone(),
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z_i1.clone(),
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)?;
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augmented_F_circuit = AugmentedFCircuit::<C1, FC> {
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poseidon_config: self.poseidon_config.clone(),
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i: Some(self.i),
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z_0: Some(self.z_0.clone()),
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z_i: Some(self.z_i.clone()),
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u_i: Some(self.u_i.clone()),
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U_i: Some(self.U_i.clone()),
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U_i1: Some(U_i1.clone()),
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cmT: Some(cmT),
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F: self.F,
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x: Some(u_i1_x),
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};
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}
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let cs = ConstraintSystem::<C1::ScalarField>::new_ref();
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augmented_F_circuit.generate_constraints(cs.clone())?;
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let cs = cs.into_inner().ok_or(Error::NoInnerConstraintSystem)?;
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// notice that here we use 'Z' (uppercase) to denote the 'z-vector' as in the paper, not
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// the value 'z' (lowercase) which is the state
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let Z_i1 = extract_z::<C1::ScalarField>(&cs);
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let (w_i1, x_i1) = self.r1cs.split_z(&Z_i1);
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assert_eq!(x_i1.len(), 1);
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assert_eq!(x_i1[0], u_i1_x);
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// compute committed instances, w_{i+1}, u_{i+1}, which will be used as w_i, u_i, so we
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// assign them directly to w_i, u_i.
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self.w_i = Witness::<C1>::new(w_i1.clone(), self.r1cs.A.n_rows);
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self.u_i = self.w_i.commit(&self.pedersen_params, vec![u_i1_x])?;
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// set values for next iteration
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self.i += C1::ScalarField::one();
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self.z_i = z_i1.clone();
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self.U_i = U_i1.clone();
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self.W_i = W_i1.clone();
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Ok(())
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}
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/// Implements IVC.V
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pub fn verify(&mut self, z_0: Vec<C1::ScalarField>, num_steps: u32) -> Result<(), Error> {
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if self.i != C1::ScalarField::from(num_steps) {
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return Err(Error::IVCVerificationFail);
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}
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if self.u_i.x.len() != 1 || self.U_i.x.len() != 1 {
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return Err(Error::IVCVerificationFail);
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}
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// check that u_i's output points to the running instance
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// u_i.X == H(i, z_0, z_i, U_i)
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let expected_u_i_x = self
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.U_i
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.hash(&self.poseidon_config, self.i, z_0, self.z_i.clone())?;
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if expected_u_i_x != self.u_i.x[0] {
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return Err(Error::IVCVerificationFail);
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}
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// check u_i.cmE==0, u_i.u==1 (=u_i is a un-relaxed instance)
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if self.u_i.cmE != C1::zero() || self.u_i.u != C1::ScalarField::one() {
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return Err(Error::IVCVerificationFail);
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}
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// check R1CS satisfiability
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self.r1cs.check_instance_relation(&self.w_i, &self.u_i)?;
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// check RelaxedR1CS satisfiability
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self.r1cs
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.check_relaxed_instance_relation(&self.W_i, &self.U_i)?;
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Ok(())
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use ark_pallas::{Fr, Projective};
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use ark_vesta::Projective as Projective2;
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use crate::folding::nova::circuits::tests::TestFCircuit;
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use crate::transcript::poseidon::tests::poseidon_test_config;
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#[test]
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fn test_ivc() {
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let mut rng = ark_std::test_rng();
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let poseidon_config = poseidon_test_config::<Fr>();
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let F_circuit = TestFCircuit::<Fr>::new();
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let z_0 = vec![Fr::from(3_u32)];
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let mut ivc = IVC::<Projective, Projective2, TestFCircuit<Fr>>::new(
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&mut rng,
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poseidon_config, // poseidon config
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F_circuit,
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z_0.clone(),
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)
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.unwrap();
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let num_steps: usize = 3;
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for _ in 0..num_steps {
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ivc.prove_step().unwrap();
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}
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ivc.verify(z_0, num_steps as u32).unwrap();
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}
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}
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@ -0,0 +1,67 @@ |
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use ark_crypto_primitives::sponge::Absorb;
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use ark_ec::{CurveGroup, Group};
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use ark_std::{One, Zero};
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use super::{CommittedInstance, Witness};
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use crate::ccs::r1cs::R1CS;
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use crate::Error;
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/// NovaR1CS extends R1CS methods with Nova specific methods
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pub trait NovaR1CS<C: CurveGroup> {
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/// returns a dummy instance (Witness and CommittedInstance) for the current R1CS structure
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fn dummy_instance(&self) -> (Witness<C>, CommittedInstance<C>);
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/// checks the R1CS relation (un-relaxed) for the given Witness and CommittedInstance.
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fn check_instance_relation(
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&self,
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W: &Witness<C>,
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U: &CommittedInstance<C>,
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) -> Result<(), Error>;
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/// checks the Relaxed R1CS relation (corresponding to the current R1CS) for the given Witness
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/// and CommittedInstance.
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fn check_relaxed_instance_relation(
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&self,
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W: &Witness<C>,
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U: &CommittedInstance<C>,
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) -> Result<(), Error>;
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}
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impl<C: CurveGroup> NovaR1CS<C> for R1CS<C::ScalarField>
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where
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<C as Group>::ScalarField: Absorb,
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<C as ark_ec::CurveGroup>::BaseField: ark_ff::PrimeField,
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{
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fn dummy_instance(&self) -> (Witness<C>, CommittedInstance<C>) {
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let w_len = self.A.n_cols - 1 - self.l;
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let w_dummy = Witness::<C>::new(vec![C::ScalarField::zero(); w_len], self.A.n_rows);
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let u_dummy = CommittedInstance::<C>::dummy(self.l);
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(w_dummy, u_dummy)
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}
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fn check_instance_relation(
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&self,
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W: &Witness<C>,
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U: &CommittedInstance<C>,
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) -> Result<(), Error> {
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if U.cmE != C::zero() || U.u != C::ScalarField::one() {
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return Err(Error::R1CSUnrelaxedFail);
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}
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let Z: Vec<C::ScalarField> = [vec![U.u], U.x.to_vec(), W.W.to_vec()].concat();
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self.check_relation(&Z)
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}
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fn check_relaxed_instance_relation(
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&self,
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W: &Witness<C>,
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U: &CommittedInstance<C>,
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) -> Result<(), Error> {
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let mut rel_r1cs = self.clone().relax();
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rel_r1cs.u = U.u;
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rel_r1cs.E = W.E.clone();
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let Z: Vec<C::ScalarField> = [vec![U.u], U.x.to_vec(), W.W.to_vec()].concat();
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rel_r1cs.check_relation(&Z)
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}
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}
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