sonobe/folding-schemes/src/folding/nova/decider_eth.rs
folding-schemes/src/folding/nova/decider_eth.rsRaw
1/// This file implements the onchain (Ethereum's EVM) decider.
2use ark_bn254::Bn254;
3use ark_crypto_primitives::sponge::Absorb;
4use ark_ec::{AffineRepr, CurveGroup, Group};
5use ark_ff::{BigInteger, PrimeField};
6use ark_groth16::Groth16;
7use ark_r1cs_std::{groups::GroupOpsBounds, prelude::CurveVar, ToConstraintFieldGadget};
8use ark_snark::SNARK;
9use ark_std::rand::{CryptoRng, RngCore};
10use ark_std::{One, Zero};
11use core::marker::PhantomData;
12
13pub use super::decider_eth_circuit::{DeciderEthCircuit, KZGChallengesGadget};
14use super::{nifs::NIFS, CommittedInstance, Nova};
15use crate::commitment::{
16 kzg::{Proof as KZGProof, KZG},
17 pedersen::Params as PedersenParams,
18 CommitmentScheme,
19};
20use crate::folding::circuits::{nonnative::affine::NonNativeAffineVar, CF2};
21use crate::frontend::FCircuit;
22use crate::Error;
23use crate::{Decider as DeciderTrait, FoldingScheme};
24
25#[derive(Debug, Clone, Eq, PartialEq)]
26pub struct Proof<C1, CS1, S>
27where
28 C1: CurveGroup,
29 CS1: CommitmentScheme<C1, ProverChallenge = C1::ScalarField, Challenge = C1::ScalarField>,
30 S: SNARK<C1::ScalarField>,
31{
32 snark_proof: S::Proof,
33 kzg_proofs: [CS1::Proof; 2],
34 // cmT and r are values for the last fold, U_{i+1}=NIFS.V(r, U_i, u_i, cmT), and they are
35 // checked in-circuit
36 cmT: C1,
37 r: C1::ScalarField,
38 // the KZG challenges are provided by the prover, but in-circuit they are checked to match
39 // the in-circuit computed computed ones.
40 kzg_challenges: [C1::ScalarField; 2],
41}
42
43/// Onchain Decider, for ethereum use cases
44#[derive(Clone, Debug)]
45pub struct Decider<C1, GC1, C2, GC2, FC, CS1, CS2, S, FS> {
46 _c1: PhantomData<C1>,
47 _gc1: PhantomData<GC1>,
48 _c2: PhantomData<C2>,
49 _gc2: PhantomData<GC2>,
50 _fc: PhantomData<FC>,
51 _cs1: PhantomData<CS1>,
52 _cs2: PhantomData<CS2>,
53 _s: PhantomData<S>,
54 _fs: PhantomData<FS>,
55}
56
57impl<C1, GC1, C2, GC2, FC, CS1, CS2, S, FS> DeciderTrait<C1, C2, FC, FS>
58 for Decider<C1, GC1, C2, GC2, FC, CS1, CS2, S, FS>
59where
60 C1: CurveGroup,
61 C2: CurveGroup,
62 GC1: CurveVar<C1, CF2<C1>> + ToConstraintFieldGadget<CF2<C1>>,
63 GC2: CurveVar<C2, CF2<C2>> + ToConstraintFieldGadget<CF2<C2>>,
64 FC: FCircuit<C1::ScalarField>,
65 // CS1 is a KZG commitment, where challenge is C1::Fr elem
66 CS1: CommitmentScheme<
67 C1,
68 ProverChallenge = C1::ScalarField,
69 Challenge = C1::ScalarField,
70 Proof = KZGProof<C1>,
71 >,
72 // enforce that the CS2 is Pedersen commitment scheme, since we're at Ethereum's EVM decider
73 CS2: CommitmentScheme<C2, ProverParams = PedersenParams<C2>>,
74 S: SNARK<C1::ScalarField>,
75 FS: FoldingScheme<C1, C2, FC>,
76 <C1 as CurveGroup>::BaseField: PrimeField,
77 <C2 as CurveGroup>::BaseField: PrimeField,
78 <C1 as Group>::ScalarField: Absorb,
79 <C2 as Group>::ScalarField: Absorb,
80 C1: CurveGroup<BaseField = C2::ScalarField, ScalarField = C2::BaseField>,
81 for<'b> &'b GC1: GroupOpsBounds<'b, C1, GC1>,
82 for<'b> &'b GC2: GroupOpsBounds<'b, C2, GC2>,
83 // constrain FS into Nova, since this is a Decider specifically for Nova
84 Nova<C1, GC1, C2, GC2, FC, CS1, CS2>: From<FS>,
85 crate::folding::nova::ProverParams<C1, C2, CS1, CS2>:
86 From<<FS as FoldingScheme<C1, C2, FC>>::ProverParam>,
87 crate::folding::nova::VerifierParams<C1, C2, CS1, CS2>:
88 From<<FS as FoldingScheme<C1, C2, FC>>::VerifierParam>,
89{
90 type PreprocessorParam = (FS::ProverParam, FS::VerifierParam);
91 type ProverParam = (S::ProvingKey, CS1::ProverParams);
92 type Proof = Proof<C1, CS1, S>;
93 /// VerifierParam = (pp_hash, snark::vk, commitment_scheme::vk)
94 type VerifierParam = (C1::ScalarField, S::VerifyingKey, CS1::VerifierParams);
95 type PublicInput = Vec<C1::ScalarField>;
96 type CommittedInstance = CommittedInstance<C1>;
97
98 fn preprocess(
99 mut rng: impl RngCore + CryptoRng,
100 prep_param: &Self::PreprocessorParam,
101 fs: FS,
102 ) -> Result<(Self::ProverParam, Self::VerifierParam), Error> {
103 let circuit =
104 DeciderEthCircuit::<C1, GC1, C2, GC2, CS1, CS2>::from_nova::<FC>(fs.into()).unwrap();
105
106 // get the Groth16 specific setup for the circuit
107 let (g16_pk, g16_vk) = S::circuit_specific_setup(circuit, &mut rng).unwrap();
108
109 // get the FoldingScheme prover & verifier params from Nova
110 #[allow(clippy::type_complexity)]
111 let nova_pp:
112 <Nova<C1, GC1, C2, GC2, FC, CS1, CS2> as FoldingScheme<C1, C2, FC>>::ProverParam =
113 prep_param.0.clone().into()
114 ;
115 #[allow(clippy::type_complexity)]
116 let nova_vp:
117 <Nova<C1, GC1, C2, GC2, FC, CS1, CS2> as FoldingScheme<C1, C2, FC>>::VerifierParam =
118 prep_param.1.clone().into();
119 let pp_hash = nova_vp.pp_hash()?;
120
121 let pp = (g16_pk, nova_pp.cs_pp);
122 let vp = (pp_hash, g16_vk, nova_vp.cs_vp);
123 Ok((pp, vp))
124 }
125
126 fn prove(
127 mut rng: impl RngCore + CryptoRng,
128 pp: Self::ProverParam,
129 folding_scheme: FS,
130 ) -> Result<Self::Proof, Error> {
131 let (snark_pk, cs_pk): (S::ProvingKey, CS1::ProverParams) = pp;
132
133 let circuit = DeciderEthCircuit::<C1, GC1, C2, GC2, CS1, CS2>::from_nova::<FC>(
134 folding_scheme.into(),
135 )?;
136
137 let snark_proof = S::prove(&snark_pk, circuit.clone(), &mut rng)
138 .map_err(|e| Error::Other(e.to_string()))?;
139
140 let cmT = circuit.cmT.unwrap();
141 let r_Fr = circuit.r.unwrap();
142 let W_i1 = circuit.W_i1.unwrap();
143
144 // get the challenges that have been already computed when preparing the circuit inputs in
145 // the above `from_nova` call
146 let challenge_W = circuit
147 .kzg_c_W
148 .ok_or(Error::MissingValue("kzg_c_W".to_string()))?;
149 let challenge_E = circuit
150 .kzg_c_E
151 .ok_or(Error::MissingValue("kzg_c_E".to_string()))?;
152
153 // generate KZG proofs
154 let U_cmW_proof = CS1::prove_with_challenge(
155 &cs_pk,
156 challenge_W,
157 &W_i1.W,
158 &C1::ScalarField::zero(),
159 None,
160 )?;
161 let U_cmE_proof = CS1::prove_with_challenge(
162 &cs_pk,
163 challenge_E,
164 &W_i1.E,
165 &C1::ScalarField::zero(),
166 None,
167 )?;
168
169 Ok(Self::Proof {
170 snark_proof,
171 kzg_proofs: [U_cmW_proof, U_cmE_proof],
172 cmT,
173 r: r_Fr,
174 kzg_challenges: [challenge_W, challenge_E],
175 })
176 }
177
178 fn verify(
179 vp: Self::VerifierParam,
180 i: C1::ScalarField,
181 z_0: Vec<C1::ScalarField>,
182 z_i: Vec<C1::ScalarField>,
183 running_instance: &Self::CommittedInstance,
184 incoming_instance: &Self::CommittedInstance,
185 proof: &Self::Proof,
186 ) -> Result<bool, Error> {
187 if i <= C1::ScalarField::one() {
188 return Err(Error::NotEnoughSteps);
189 }
190
191 let (pp_hash, snark_vk, cs_vk): (C1::ScalarField, S::VerifyingKey, CS1::VerifierParams) =
192 vp;
193
194 // compute U = U_{d+1}= NIFS.V(U_d, u_d, cmT)
195 let U = NIFS::<C1, CS1>::verify(proof.r, running_instance, incoming_instance, &proof.cmT);
196
197 let (cmE_x, cmE_y) = NonNativeAffineVar::inputize(U.cmE)?;
198 let (cmW_x, cmW_y) = NonNativeAffineVar::inputize(U.cmW)?;
199 let (cmT_x, cmT_y) = NonNativeAffineVar::inputize(proof.cmT)?;
200
201 let public_input: Vec<C1::ScalarField> = vec![
202 vec![pp_hash, i],
203 z_0,
204 z_i,
205 vec![U.u],
206 U.x.clone(),
207 cmE_x,
208 cmE_y,
209 cmW_x,
210 cmW_y,
211 proof.kzg_challenges.to_vec(),
212 vec![
213 proof.kzg_proofs[0].eval, // eval_W
214 proof.kzg_proofs[1].eval, // eval_E
215 ],
216 cmT_x,
217 cmT_y,
218 vec![proof.r],
219 ]
220 .concat();
221
222 let snark_v = S::verify(&snark_vk, &public_input, &proof.snark_proof)
223 .map_err(|e| Error::Other(e.to_string()))?;
224 if !snark_v {
225 return Err(Error::SNARKVerificationFail);
226 }
227
228 // we're at the Ethereum EVM case, so the CS1 is KZG commitments
229 CS1::verify_with_challenge(
230 &cs_vk,
231 proof.kzg_challenges[0],
232 &U.cmW,
233 &proof.kzg_proofs[0],
234 )?;
235 CS1::verify_with_challenge(
236 &cs_vk,
237 proof.kzg_challenges[1],
238 &U.cmE,
239 &proof.kzg_proofs[1],
240 )?;
241
242 Ok(true)
243 }
244}
245
246/// Prepares solidity calldata for calling the NovaDecider contract
247pub fn prepare_calldata(
248 function_signature_check: [u8; 4],
249 i: ark_bn254::Fr,
250 z_0: Vec<ark_bn254::Fr>,
251 z_i: Vec<ark_bn254::Fr>,
252 running_instance: &CommittedInstance<ark_bn254::G1Projective>,
253 incoming_instance: &CommittedInstance<ark_bn254::G1Projective>,
254 proof: Proof<ark_bn254::G1Projective, KZG<'static, Bn254>, Groth16<Bn254>>,
255) -> Result<Vec<u8>, Error> {
256 Ok(vec![
257 function_signature_check.to_vec(),
258 i.into_bigint().to_bytes_be(), // i
259 z_0.iter()
260 .flat_map(|v| v.into_bigint().to_bytes_be())
261 .collect::<Vec<u8>>(), // z_0
262 z_i.iter()
263 .flat_map(|v| v.into_bigint().to_bytes_be())
264 .collect::<Vec<u8>>(), // z_i
265 point_to_eth_format(running_instance.cmW.into_affine())?, // U_i_cmW
266 point_to_eth_format(running_instance.cmE.into_affine())?, // U_i_cmE
267 running_instance.u.into_bigint().to_bytes_be(), // U_i_u
268 incoming_instance.u.into_bigint().to_bytes_be(), // u_i_u
269 proof.r.into_bigint().to_bytes_be(), // r
270 running_instance
271 .x
272 .iter()
273 .flat_map(|v| v.into_bigint().to_bytes_be())
274 .collect::<Vec<u8>>(), // U_i_x
275 point_to_eth_format(incoming_instance.cmW.into_affine())?, // u_i_cmW
276 incoming_instance
277 .x
278 .iter()
279 .flat_map(|v| v.into_bigint().to_bytes_be())
280 .collect::<Vec<u8>>(), // u_i_x
281 point_to_eth_format(proof.cmT.into_affine())?, // cmT
282 point_to_eth_format(proof.snark_proof.a)?, // pA
283 point2_to_eth_format(proof.snark_proof.b)?, // pB
284 point_to_eth_format(proof.snark_proof.c)?, // pC
285 proof.kzg_challenges[0].into_bigint().to_bytes_be(), // challenge_W
286 proof.kzg_challenges[1].into_bigint().to_bytes_be(), // challenge_E
287 proof.kzg_proofs[0].eval.into_bigint().to_bytes_be(), // eval W
288 proof.kzg_proofs[1].eval.into_bigint().to_bytes_be(), // eval E
289 point_to_eth_format(proof.kzg_proofs[0].proof.into_affine())?, // W kzg_proof
290 point_to_eth_format(proof.kzg_proofs[1].proof.into_affine())?, // E kzg_proof
291 ]
292 .concat())
293}
294
295fn point_to_eth_format<C: AffineRepr>(p: C) -> Result<Vec<u8>, Error>
296where
297 C::BaseField: PrimeField,
298{
299 // the encoding of the additive identity is [0, 0] on the EVM
300 let zero_point = (&C::BaseField::zero(), &C::BaseField::zero());
301 let (x, y) = p.xy().unwrap_or(zero_point);
302
303 Ok([x.into_bigint().to_bytes_be(), y.into_bigint().to_bytes_be()].concat())
304}
305fn point2_to_eth_format(p: ark_bn254::G2Affine) -> Result<Vec<u8>, Error> {
306 let zero_point = (&ark_bn254::Fq2::zero(), &ark_bn254::Fq2::zero());
307 let (x, y) = p.xy().unwrap_or(zero_point);
308
309 Ok([
310 x.c1.into_bigint().to_bytes_be(),
311 x.c0.into_bigint().to_bytes_be(),
312 y.c1.into_bigint().to_bytes_be(),
313 y.c0.into_bigint().to_bytes_be(),
314 ]
315 .concat())
316}
317
318#[cfg(test)]
319pub mod tests {
320 use ark_bn254::{constraints::GVar, Fr, G1Projective as Projective};
321 use ark_grumpkin::{constraints::GVar as GVar2, Projective as Projective2};
322 use std::time::Instant;
323
324 use super::*;
325 use crate::commitment::pedersen::Pedersen;
326 use crate::folding::nova::PreprocessorParam;
327 use crate::frontend::tests::CubicFCircuit;
328 use crate::transcript::poseidon::poseidon_canonical_config;
329
330 #[test]
331 fn test_decider() {
332 // use Nova as FoldingScheme
333 type N = Nova<
334 Projective,
335 GVar,
336 Projective2,
337 GVar2,
338 CubicFCircuit<Fr>,
339 KZG<'static, Bn254>,
340 Pedersen<Projective2>,
341 >;
342 type D = Decider<
343 Projective,
344 GVar,
345 Projective2,
346 GVar2,
347 CubicFCircuit<Fr>,
348 KZG<'static, Bn254>,
349 Pedersen<Projective2>,
350 Groth16<Bn254>, // here we define the Snark to use in the decider
351 N, // here we define the FoldingScheme to use
352 >;
353
354 let mut rng = ark_std::test_rng();
355 let poseidon_config = poseidon_canonical_config::<Fr>();
356
357 let F_circuit = CubicFCircuit::<Fr>::new(()).unwrap();
358 let z_0 = vec![Fr::from(3_u32)];
359
360 let prep_param = PreprocessorParam::new(poseidon_config, F_circuit);
361 let nova_params = N::preprocess(&mut rng, &prep_param).unwrap();
362
363 let start = Instant::now();
364 let mut nova = N::init(nova_params.clone(), F_circuit, z_0.clone()).unwrap();
365 println!("Nova initialized, {:?}", start.elapsed());
366 let start = Instant::now();
367 nova.prove_step(&mut rng, vec![]).unwrap();
368 println!("prove_step, {:?}", start.elapsed());
369 nova.prove_step(&mut rng, vec![]).unwrap(); // do a 2nd step
370
371 let mut rng = rand::rngs::OsRng;
372
373 // prepare the Decider prover & verifier params
374 let (decider_pp, decider_vp) = D::preprocess(&mut rng, &nova_params, nova.clone()).unwrap();
375
376 // decider proof generation
377 let start = Instant::now();
378 let proof = D::prove(rng, decider_pp, nova.clone()).unwrap();
379 println!("Decider prove, {:?}", start.elapsed());
380
381 // decider proof verification
382 let start = Instant::now();
383 let verified = D::verify(
384 decider_vp, nova.i, nova.z_0, nova.z_i, &nova.U_i, &nova.u_i, &proof,
385 )
386 .unwrap();
387 assert!(verified);
388 println!("Decider verify, {:?}", start.elapsed());
389 }
390}