sonobe/folding-schemes/src/folding/nova/decider_eth_circuit.rs
folding-schemes/src/folding/nova/decider_eth_circuit.rsRaw
1/// This file implements the onchain (Ethereum's EVM) decider circuit. For non-ethereum use cases,
2/// other more efficient approaches can be used.
3/// More details can be found at the documentation page:
4/// https://privacy-scaling-explorations.github.io/sonobe-docs/design/nova-decider-onchain.html
5use ark_crypto_primitives::sponge::{
6 constraints::CryptographicSpongeVar,
7 poseidon::{constraints::PoseidonSpongeVar, PoseidonConfig, PoseidonSponge},
8 Absorb, CryptographicSponge,
9};
10use ark_ec::{CurveGroup, Group};
11use ark_ff::{BigInteger, PrimeField};
12use ark_poly::Polynomial;
13use ark_r1cs_std::{
14 alloc::{AllocVar, AllocationMode},
15 boolean::Boolean,
16 eq::EqGadget,
17 fields::{fp::FpVar, FieldVar},
18 groups::GroupOpsBounds,
19 poly::{domain::Radix2DomainVar, evaluations::univariate::EvaluationsVar},
20 prelude::CurveVar,
21 ToConstraintFieldGadget,
22};
23use ark_relations::r1cs::{ConstraintSynthesizer, ConstraintSystemRef, Namespace, SynthesisError};
24use ark_std::{log2, Zero};
25use core::{borrow::Borrow, marker::PhantomData};
26
27use super::{
28 circuits::{ChallengeGadget, CommittedInstanceVar},
29 nifs::{nova::NIFS, NIFSTrait},
30 CommittedInstance, Nova, Witness,
31};
32use crate::commitment::{pedersen::Params as PedersenParams, CommitmentScheme};
33use crate::folding::circuits::{
34 cyclefold::{CycleFoldCommittedInstance, CycleFoldWitness},
35 nonnative::{affine::NonNativeAffineVar, uint::NonNativeUintVar},
36 CF1, CF2,
37};
38use crate::frontend::FCircuit;
39use crate::transcript::{Transcript, TranscriptVar};
40use crate::utils::{
41 gadgets::{MatrixGadget, SparseMatrixVar, VectorGadget},
42 vec::poly_from_vec,
43};
44use crate::Error;
45use crate::{
46 arith::r1cs::R1CS,
47 folding::traits::{CommittedInstanceVarOps, Dummy, WitnessVarOps},
48};
49
50#[derive(Debug, Clone)]
51pub struct RelaxedR1CSGadget {}
52impl RelaxedR1CSGadget {
53 /// performs the RelaxedR1CS check for native variables (Az∘Bz==uCz+E)
54 pub fn check_native<F: PrimeField>(
55 r1cs: R1CSVar<F, F, FpVar<F>>,
56 E: Vec<FpVar<F>>,
57 u: FpVar<F>,
58 z: Vec<FpVar<F>>,
59 ) -> Result<(), SynthesisError> {
60 let Az = r1cs.A.mul_vector(&z)?;
61 let Bz = r1cs.B.mul_vector(&z)?;
62 let Cz = r1cs.C.mul_vector(&z)?;
63 let uCzE = Cz.mul_scalar(&u)?.add(&E)?;
64 let AzBz = Az.hadamard(&Bz)?;
65 AzBz.enforce_equal(&uCzE)?;
66 Ok(())
67 }
68
69 /// performs the RelaxedR1CS check for non-native variables (Az∘Bz==uCz+E)
70 pub fn check_nonnative<F: PrimeField, CF: PrimeField>(
71 r1cs: R1CSVar<F, CF, NonNativeUintVar<CF>>,
72 E: Vec<NonNativeUintVar<CF>>,
73 u: NonNativeUintVar<CF>,
74 z: Vec<NonNativeUintVar<CF>>,
75 ) -> Result<(), SynthesisError> {
76 // First we do addition and multiplication without mod F's order
77 let Az = r1cs.A.mul_vector(&z)?;
78 let Bz = r1cs.B.mul_vector(&z)?;
79 let Cz = r1cs.C.mul_vector(&z)?;
80 let uCzE = Cz.mul_scalar(&u)?.add(&E)?;
81 let AzBz = Az.hadamard(&Bz)?;
82
83 // Then we compare the results by checking if they are congruent
84 // modulo the field order
85 AzBz.into_iter()
86 .zip(uCzE)
87 .try_for_each(|(a, b)| a.enforce_congruent::<F>(&b))
88 }
89}
90
91#[derive(Debug, Clone)]
92pub struct R1CSVar<F: PrimeField, CF: PrimeField, FV: AllocVar<F, CF>> {
93 _f: PhantomData<F>,
94 _cf: PhantomData<CF>,
95 _fv: PhantomData<FV>,
96 pub A: SparseMatrixVar<F, CF, FV>,
97 pub B: SparseMatrixVar<F, CF, FV>,
98 pub C: SparseMatrixVar<F, CF, FV>,
99}
100
101impl<F, CF, FV> AllocVar<R1CS<F>, CF> for R1CSVar<F, CF, FV>
102where
103 F: PrimeField,
104 CF: PrimeField,
105 FV: AllocVar<F, CF>,
106{
107 fn new_variable<T: Borrow<R1CS<F>>>(
108 cs: impl Into<Namespace<CF>>,
109 f: impl FnOnce() -> Result<T, SynthesisError>,
110 _mode: AllocationMode,
111 ) -> Result<Self, SynthesisError> {
112 f().and_then(|val| {
113 let cs = cs.into();
114
115 let A = SparseMatrixVar::<F, CF, FV>::new_constant(cs.clone(), &val.borrow().A)?;
116 let B = SparseMatrixVar::<F, CF, FV>::new_constant(cs.clone(), &val.borrow().B)?;
117 let C = SparseMatrixVar::<F, CF, FV>::new_constant(cs.clone(), &val.borrow().C)?;
118
119 Ok(Self {
120 _f: PhantomData,
121 _cf: PhantomData,
122 _fv: PhantomData,
123 A,
124 B,
125 C,
126 })
127 })
128 }
129}
130
131/// In-circuit representation of the Witness associated to the CommittedInstance.
132#[derive(Debug, Clone)]
133pub struct WitnessVar<C: CurveGroup> {
134 pub E: Vec<FpVar<C::ScalarField>>,
135 pub rE: FpVar<C::ScalarField>,
136 pub W: Vec<FpVar<C::ScalarField>>,
137 pub rW: FpVar<C::ScalarField>,
138}
139
140impl<C> AllocVar<Witness<C>, CF1<C>> for WitnessVar<C>
141where
142 C: CurveGroup,
143{
144 fn new_variable<T: Borrow<Witness<C>>>(
145 cs: impl Into<Namespace<CF1<C>>>,
146 f: impl FnOnce() -> Result<T, SynthesisError>,
147 mode: AllocationMode,
148 ) -> Result<Self, SynthesisError> {
149 f().and_then(|val| {
150 let cs = cs.into();
151
152 let E: Vec<FpVar<C::ScalarField>> =
153 Vec::new_variable(cs.clone(), || Ok(val.borrow().E.clone()), mode)?;
154 let rE =
155 FpVar::<C::ScalarField>::new_variable(cs.clone(), || Ok(val.borrow().rE), mode)?;
156
157 let W: Vec<FpVar<C::ScalarField>> =
158 Vec::new_variable(cs.clone(), || Ok(val.borrow().W.clone()), mode)?;
159 let rW =
160 FpVar::<C::ScalarField>::new_variable(cs.clone(), || Ok(val.borrow().rW), mode)?;
161
162 Ok(Self { E, rE, W, rW })
163 })
164 }
165}
166
167impl<C: CurveGroup> WitnessVarOps<C::ScalarField> for WitnessVar<C> {
168 fn get_openings(&self) -> Vec<(&[FpVar<C::ScalarField>], FpVar<C::ScalarField>)> {
169 vec![(&self.E, self.rE.clone()), (&self.W, self.rW.clone())]
170 }
171}
172
173/// Circuit that implements the in-circuit checks needed for the onchain (Ethereum's EVM)
174/// verification.
175#[derive(Clone, Debug)]
176pub struct DeciderEthCircuit<C1, GC1, C2, GC2, CS1, CS2, const H: bool = false>
177where
178 C1: CurveGroup,
179 GC1: CurveVar<C1, CF2<C1>>,
180 C2: CurveGroup,
181 GC2: CurveVar<C2, CF2<C2>>,
182 CS1: CommitmentScheme<C1, H>,
183 CS2: CommitmentScheme<C2, H>,
184{
185 _c1: PhantomData<C1>,
186 _gc1: PhantomData<GC1>,
187 _c2: PhantomData<C2>,
188 _gc2: PhantomData<GC2>,
189 _cs1: PhantomData<CS1>,
190 _cs2: PhantomData<CS2>,
191
192 /// E vector's length of the Nova instance witness
193 pub E_len: usize,
194 /// E vector's length of the CycleFold instance witness
195 pub cf_E_len: usize,
196 /// R1CS of the Augmented Function circuit
197 pub r1cs: R1CS<C1::ScalarField>,
198 /// R1CS of the CycleFold circuit
199 pub cf_r1cs: R1CS<C2::ScalarField>,
200 /// CycleFold PedersenParams over C2
201 pub cf_pedersen_params: PedersenParams<C2>,
202 pub poseidon_config: PoseidonConfig<CF1<C1>>,
203 /// public params hash
204 pub pp_hash: Option<C1::ScalarField>,
205 pub i: Option<CF1<C1>>,
206 /// initial state
207 pub z_0: Option<Vec<C1::ScalarField>>,
208 /// current i-th state
209 pub z_i: Option<Vec<C1::ScalarField>>,
210 /// Nova instances
211 pub u_i: Option<CommittedInstance<C1>>,
212 pub w_i: Option<Witness<C1>>,
213 pub U_i: Option<CommittedInstance<C1>>,
214 pub W_i: Option<Witness<C1>>,
215 pub U_i1: Option<CommittedInstance<C1>>,
216 pub W_i1: Option<Witness<C1>>,
217 pub cmT: Option<C1>,
218 pub r: Option<C1::ScalarField>,
219 /// CycleFold running instance
220 pub cf_U_i: Option<CycleFoldCommittedInstance<C2>>,
221 pub cf_W_i: Option<CycleFoldWitness<C2>>,
222
223 /// KZG challenges
224 pub kzg_c_W: Option<C1::ScalarField>,
225 pub kzg_c_E: Option<C1::ScalarField>,
226 pub eval_W: Option<C1::ScalarField>,
227 pub eval_E: Option<C1::ScalarField>,
228}
229impl<C1, GC1, C2, GC2, CS1, CS2, const H: bool> DeciderEthCircuit<C1, GC1, C2, GC2, CS1, CS2, H>
230where
231 C1: CurveGroup,
232 C2: CurveGroup,
233 GC1: CurveVar<C1, CF2<C1>> + ToConstraintFieldGadget<CF2<C1>>,
234 GC2: CurveVar<C2, CF2<C2>> + ToConstraintFieldGadget<CF2<C2>>,
235 CS1: CommitmentScheme<C1, H>,
236 // enforce that the CS2 is Pedersen commitment scheme, since we're at Ethereum's EVM decider
237 CS2: CommitmentScheme<C2, H, ProverParams = PedersenParams<C2>>,
238 <C1 as Group>::ScalarField: Absorb,
239 <C1 as CurveGroup>::BaseField: PrimeField,
240{
241 /// returns an instance of the DeciderEthCircuit from the given Nova struct
242 pub fn from_nova<FC: FCircuit<C1::ScalarField>>(
243 nova: Nova<C1, GC1, C2, GC2, FC, CS1, CS2, H>,
244 ) -> Result<Self, Error> {
245 let mut transcript = PoseidonSponge::<C1::ScalarField>::new(&nova.poseidon_config);
246
247 // compute the U_{i+1}, W_{i+1}
248 let (W_i1, U_i1, cmT, r_bits) = NIFS::<C1, CS1, PoseidonSponge<C1::ScalarField>, H>::prove(
249 &nova.cs_pp,
250 &nova.r1cs.clone(),
251 &mut transcript,
252 nova.pp_hash,
253 &nova.W_i,
254 &nova.U_i,
255 &nova.w_i,
256 &nova.u_i,
257 )?;
258 let r_Fr = C1::ScalarField::from_bigint(BigInteger::from_bits_le(&r_bits))
259 .ok_or(Error::OutOfBounds)?;
260
261 // compute the KZG challenges used as inputs in the circuit
262 let (kzg_challenge_W, kzg_challenge_E) =
263 KZGChallengesGadget::<C1>::get_challenges_native(&mut transcript, U_i1.clone());
264
265 // get KZG evals
266 let mut W = W_i1.W.clone();
267 W.extend(
268 std::iter::repeat(C1::ScalarField::zero())
269 .take(W_i1.W.len().next_power_of_two() - W_i1.W.len()),
270 );
271 let mut E = W_i1.E.clone();
272 E.extend(
273 std::iter::repeat(C1::ScalarField::zero())
274 .take(W_i1.E.len().next_power_of_two() - W_i1.E.len()),
275 );
276 let p_W = poly_from_vec(W.to_vec())?;
277 let eval_W = p_W.evaluate(&kzg_challenge_W);
278 let p_E = poly_from_vec(E.to_vec())?;
279 let eval_E = p_E.evaluate(&kzg_challenge_E);
280
281 Ok(Self {
282 _c1: PhantomData,
283 _gc1: PhantomData,
284 _c2: PhantomData,
285 _gc2: PhantomData,
286 _cs1: PhantomData,
287 _cs2: PhantomData,
288
289 E_len: nova.W_i.E.len(),
290 cf_E_len: nova.cf_W_i.E.len(),
291 r1cs: nova.r1cs,
292 cf_r1cs: nova.cf_r1cs,
293 cf_pedersen_params: nova.cf_cs_pp,
294 poseidon_config: nova.poseidon_config,
295 pp_hash: Some(nova.pp_hash),
296 i: Some(nova.i),
297 z_0: Some(nova.z_0),
298 z_i: Some(nova.z_i),
299 u_i: Some(nova.u_i),
300 w_i: Some(nova.w_i),
301 U_i: Some(nova.U_i),
302 W_i: Some(nova.W_i),
303 U_i1: Some(U_i1),
304 W_i1: Some(W_i1),
305 cmT: Some(cmT),
306 r: Some(r_Fr),
307 cf_U_i: Some(nova.cf_U_i),
308 cf_W_i: Some(nova.cf_W_i),
309 kzg_c_W: Some(kzg_challenge_W),
310 kzg_c_E: Some(kzg_challenge_E),
311 eval_W: Some(eval_W),
312 eval_E: Some(eval_E),
313 })
314 }
315}
316
317impl<C1, GC1, C2, GC2, CS1, CS2> ConstraintSynthesizer<CF1<C1>>
318 for DeciderEthCircuit<C1, GC1, C2, GC2, CS1, CS2>
319where
320 C1: CurveGroup,
321 C2: CurveGroup,
322 GC1: CurveVar<C1, CF2<C1>>,
323 GC2: CurveVar<C2, CF2<C2>> + ToConstraintFieldGadget<CF2<C2>>,
324 CS1: CommitmentScheme<C1>,
325 CS2: CommitmentScheme<C2>,
326 <C1 as CurveGroup>::BaseField: PrimeField,
327 <C2 as CurveGroup>::BaseField: PrimeField,
328 <C1 as Group>::ScalarField: Absorb,
329 <C2 as Group>::ScalarField: Absorb,
330 C1: CurveGroup<BaseField = C2::ScalarField, ScalarField = C2::BaseField>,
331 for<'b> &'b GC2: GroupOpsBounds<'b, C2, GC2>,
332{
333 fn generate_constraints(self, cs: ConstraintSystemRef<CF1<C1>>) -> Result<(), SynthesisError> {
334 let r1cs =
335 R1CSVar::<C1::ScalarField, CF1<C1>, FpVar<CF1<C1>>>::new_witness(cs.clone(), || {
336 Ok(self.r1cs.clone())
337 })?;
338
339 let pp_hash = FpVar::<CF1<C1>>::new_input(cs.clone(), || {
340 Ok(self.pp_hash.unwrap_or_else(CF1::<C1>::zero))
341 })?;
342 let i =
343 FpVar::<CF1<C1>>::new_input(cs.clone(), || Ok(self.i.unwrap_or_else(CF1::<C1>::zero)))?;
344 let z_0 = Vec::<FpVar<CF1<C1>>>::new_input(cs.clone(), || {
345 Ok(self.z_0.unwrap_or(vec![CF1::<C1>::zero()]))
346 })?;
347 let z_i = Vec::<FpVar<CF1<C1>>>::new_input(cs.clone(), || {
348 Ok(self.z_i.unwrap_or(vec![CF1::<C1>::zero()]))
349 })?;
350
351 let u_dummy_native = CommittedInstance::<C1>::dummy(&self.r1cs);
352 let w_dummy_native = Witness::<C1>::dummy(&self.r1cs);
353
354 let u_i = CommittedInstanceVar::<C1>::new_witness(cs.clone(), || {
355 Ok(self.u_i.unwrap_or(u_dummy_native.clone()))
356 })?;
357 let U_i = CommittedInstanceVar::<C1>::new_witness(cs.clone(), || {
358 Ok(self.U_i.unwrap_or(u_dummy_native.clone()))
359 })?;
360 // here (U_i1, W_i1) = NIFS.P( (U_i,W_i), (u_i,w_i))
361 let U_i1 = CommittedInstanceVar::<C1>::new_input(cs.clone(), || {
362 Ok(self.U_i1.unwrap_or(u_dummy_native.clone()))
363 })?;
364 let W_i1 = WitnessVar::<C1>::new_witness(cs.clone(), || {
365 Ok(self.W_i1.unwrap_or(w_dummy_native.clone()))
366 })?;
367
368 // allocate the inputs for the check 5.1
369 let kzg_c_W = FpVar::<CF1<C1>>::new_input(cs.clone(), || {
370 Ok(self.kzg_c_W.unwrap_or_else(CF1::<C1>::zero))
371 })?;
372 let kzg_c_E = FpVar::<CF1<C1>>::new_input(cs.clone(), || {
373 Ok(self.kzg_c_E.unwrap_or_else(CF1::<C1>::zero))
374 })?;
375 // allocate the inputs for the check 5.2
376 let eval_W = FpVar::<CF1<C1>>::new_input(cs.clone(), || {
377 Ok(self.eval_W.unwrap_or_else(CF1::<C1>::zero))
378 })?;
379 let eval_E = FpVar::<CF1<C1>>::new_input(cs.clone(), || {
380 Ok(self.eval_E.unwrap_or_else(CF1::<C1>::zero))
381 })?;
382
383 // `sponge` is for digest computation.
384 let sponge = PoseidonSpongeVar::<C1::ScalarField>::new(cs.clone(), &self.poseidon_config);
385 // `transcript` is for challenge generation.
386 let mut transcript = sponge.clone();
387
388 // The following enumeration of the steps matches the one used at the documentation page
389 // https://privacy-scaling-explorations.github.io/sonobe-docs/design/nova-decider-onchain.html
390
391 // 2. u_i.cmE==cm(0), u_i.u==1
392 // Here zero is the x & y coordinates of the zero point affine representation.
393 let zero = NonNativeUintVar::new_constant(cs.clone(), C1::BaseField::zero())?;
394 u_i.cmE.x.enforce_equal_unaligned(&zero)?;
395 u_i.cmE.y.enforce_equal_unaligned(&zero)?;
396 (u_i.u.is_one()?).enforce_equal(&Boolean::TRUE)?;
397
398 // 3.a u_i.x[0] == H(i, z_0, z_i, U_i)
399 let (u_i_x, U_i_vec) = U_i.clone().hash(&sponge, &pp_hash, &i, &z_0, &z_i)?;
400 (u_i.x[0]).enforce_equal(&u_i_x)?;
401
402 // 4. check RelaxedR1CS of U_{i+1}
403 let z_U1: Vec<FpVar<CF1<C1>>> =
404 [vec![U_i1.u.clone()], U_i1.x.to_vec(), W_i1.W.to_vec()].concat();
405 RelaxedR1CSGadget::check_native(r1cs, W_i1.E.clone(), U_i1.u.clone(), z_U1)?;
406
407 #[cfg(feature = "light-test")]
408 log::warn!("[WARNING]: Running with the 'light-test' feature, skipping the big part of the DeciderEthCircuit.\n Only for testing purposes.");
409
410 // The following two checks (and their respective allocations) are disabled for normal
411 // tests since they take several millions of constraints and would take several minutes
412 // (and RAM) to run the test. It is active by default, and not active only when
413 // 'light-test' feature is used.
414 #[cfg(not(feature = "light-test"))]
415 {
416 // imports here instead of at the top of the file, so we avoid having multiple
417 // `#[cfg(not(test))]`
418 use crate::commitment::pedersen::PedersenGadget;
419 use crate::folding::{
420 circuits::cyclefold::{
421 CycleFoldCommittedInstanceVar, CycleFoldConfig, CycleFoldWitnessVar,
422 },
423 nova::NovaCycleFoldConfig,
424 };
425 use ark_r1cs_std::ToBitsGadget;
426
427 let cf_u_dummy_native =
428 CycleFoldCommittedInstance::<C2>::dummy(NovaCycleFoldConfig::<C1>::IO_LEN);
429 let w_dummy_native = CycleFoldWitness::<C2>::dummy(&self.cf_r1cs);
430 let cf_U_i = CycleFoldCommittedInstanceVar::<C2, GC2>::new_witness(cs.clone(), || {
431 Ok(self.cf_U_i.unwrap_or_else(|| cf_u_dummy_native.clone()))
432 })?;
433 let cf_W_i = CycleFoldWitnessVar::<C2>::new_witness(cs.clone(), || {
434 Ok(self.cf_W_i.unwrap_or(w_dummy_native.clone()))
435 })?;
436
437 // 3.b u_i.x[1] == H(cf_U_i)
438 let (cf_u_i_x, _) = cf_U_i.clone().hash(&sponge, pp_hash.clone())?;
439 (u_i.x[1]).enforce_equal(&cf_u_i_x)?;
440
441 // 7. check Pedersen commitments of cf_U_i.{cmE, cmW}
442 let H = GC2::new_constant(cs.clone(), self.cf_pedersen_params.h)?;
443 let G = Vec::<GC2>::new_constant(cs.clone(), self.cf_pedersen_params.generators)?;
444 let cf_W_i_E_bits: Result<Vec<Vec<Boolean<CF1<C1>>>>, SynthesisError> =
445 cf_W_i.E.iter().map(|E_i| E_i.to_bits_le()).collect();
446 let cf_W_i_W_bits: Result<Vec<Vec<Boolean<CF1<C1>>>>, SynthesisError> =
447 cf_W_i.W.iter().map(|W_i| W_i.to_bits_le()).collect();
448
449 let computed_cmE = PedersenGadget::<C2, GC2>::commit(
450 H.clone(),
451 G.clone(),
452 cf_W_i_E_bits?,
453 cf_W_i.rE.to_bits_le()?,
454 )?;
455 cf_U_i.cmE.enforce_equal(&computed_cmE)?;
456 let computed_cmW =
457 PedersenGadget::<C2, GC2>::commit(H, G, cf_W_i_W_bits?, cf_W_i.rW.to_bits_le()?)?;
458 cf_U_i.cmW.enforce_equal(&computed_cmW)?;
459
460 let cf_r1cs =
461 R1CSVar::<C1::BaseField, CF1<C1>, NonNativeUintVar<CF1<C1>>>::new_witness(
462 cs.clone(),
463 || Ok(self.cf_r1cs.clone()),
464 )?;
465
466 // 6. check RelaxedR1CS of cf_U_i (CycleFold instance)
467 let cf_z_U = [vec![cf_U_i.u.clone()], cf_U_i.x.to_vec(), cf_W_i.W.to_vec()].concat();
468 RelaxedR1CSGadget::check_nonnative(cf_r1cs, cf_W_i.E, cf_U_i.u.clone(), cf_z_U)?;
469 }
470
471 // 1.1.a, 5.1. compute NIFS.V and KZG challenges.
472 // We need to ensure the order of challenge generation is the same as
473 // the native counterpart, so we first compute the challenges here and
474 // do the actual checks later.
475 let cmT =
476 NonNativeAffineVar::new_input(cs.clone(), || Ok(self.cmT.unwrap_or_else(C1::zero)))?;
477 // 1.1.a
478 let r_bits = ChallengeGadget::<C1, CommittedInstance<C1>>::get_challenge_gadget(
479 &mut transcript,
480 pp_hash,
481 U_i_vec,
482 u_i.clone(),
483 Some(cmT),
484 )?;
485 // 5.1.
486 let (incircuit_c_W, incircuit_c_E) =
487 KZGChallengesGadget::<C1>::get_challenges_gadget(&mut transcript, U_i1.clone())?;
488 incircuit_c_W.enforce_equal(&kzg_c_W)?;
489 incircuit_c_E.enforce_equal(&kzg_c_E)?;
490
491 // 5.2. check eval_W==p_W(c_W) and eval_E==p_E(c_E)
492 let incircuit_eval_W = evaluate_gadget::<CF1<C1>>(W_i1.W, incircuit_c_W)?;
493 let incircuit_eval_E = evaluate_gadget::<CF1<C1>>(W_i1.E, incircuit_c_E)?;
494 incircuit_eval_W.enforce_equal(&eval_W)?;
495 incircuit_eval_E.enforce_equal(&eval_E)?;
496
497 // 1.1.b check that the NIFS.V challenge matches the one from the public input (so we avoid
498 // the verifier computing it)
499 let r_Fr = Boolean::le_bits_to_fp_var(&r_bits)?;
500 // check that the in-circuit computed r is equal to the inputted r
501 let r =
502 FpVar::<CF1<C1>>::new_input(cs.clone(), || Ok(self.r.unwrap_or_else(CF1::<C1>::zero)))?;
503 r_Fr.enforce_equal(&r)?;
504
505 Ok(())
506 }
507}
508
509/// Interpolates the polynomial from the given vector, and then returns it's evaluation at the
510/// given point.
511#[allow(unused)] // unused while check 7 is disabled
512pub fn evaluate_gadget<F: PrimeField>(
513 mut v: Vec<FpVar<F>>,
514 point: FpVar<F>,
515) -> Result<FpVar<F>, SynthesisError> {
516 v.resize(v.len().next_power_of_two(), FpVar::zero());
517 let n = v.len() as u64;
518 let gen = F::get_root_of_unity(n).unwrap();
519 let domain = Radix2DomainVar::new(gen, log2(v.len()) as u64, FpVar::one()).unwrap();
520
521 let evaluations_var = EvaluationsVar::from_vec_and_domain(v, domain, true);
522 evaluations_var.interpolate_and_evaluate(&point)
523}
524
525/// Gadget that computes the KZG challenges, also offers the rust native implementation compatible
526/// with the gadget.
527pub struct KZGChallengesGadget<C: CurveGroup> {
528 _c: PhantomData<C>,
529}
530#[allow(clippy::type_complexity)]
531impl<C> KZGChallengesGadget<C>
532where
533 C: CurveGroup,
534 C::ScalarField: PrimeField,
535 <C as CurveGroup>::BaseField: PrimeField,
536 C::ScalarField: Absorb,
537{
538 pub fn get_challenges_native<T: Transcript<C::ScalarField>>(
539 transcript: &mut T,
540 U_i: CommittedInstance<C>,
541 ) -> (C::ScalarField, C::ScalarField) {
542 // compute the KZG challenges, which are computed in-circuit and checked that it matches
543 // the inputted one
544 transcript.absorb_nonnative(&U_i.cmW);
545 let challenge_W = transcript.get_challenge();
546 transcript.absorb_nonnative(&U_i.cmE);
547 let challenge_E = transcript.get_challenge();
548
549 (challenge_W, challenge_E)
550 }
551 // compatible with the native get_challenges_native
552 pub fn get_challenges_gadget<S: CryptographicSponge, T: TranscriptVar<CF1<C>, S>>(
553 transcript: &mut T,
554 U_i: CommittedInstanceVar<C>,
555 ) -> Result<(FpVar<C::ScalarField>, FpVar<C::ScalarField>), SynthesisError> {
556 transcript.absorb(&U_i.cmW.to_constraint_field()?)?;
557 let challenge_W = transcript.get_challenge()?;
558
559 transcript.absorb(&U_i.cmE.to_constraint_field()?)?;
560 let challenge_E = transcript.get_challenge()?;
561
562 Ok((challenge_W, challenge_E))
563 }
564}
565
566#[cfg(test)]
567pub mod tests {
568 use std::cmp::max;
569
570 use ark_crypto_primitives::crh::{
571 sha256::{
572 constraints::{Sha256Gadget, UnitVar},
573 Sha256,
574 },
575 CRHScheme, CRHSchemeGadget,
576 };
577 use ark_pallas::{constraints::GVar, Fq, Fr, Projective};
578 use ark_r1cs_std::bits::uint8::UInt8;
579 use ark_relations::r1cs::ConstraintSystem;
580 use ark_std::{
581 rand::{thread_rng, Rng},
582 UniformRand,
583 };
584 use ark_vesta::{constraints::GVar as GVar2, Projective as Projective2};
585
586 use super::*;
587 use crate::arith::{
588 r1cs::{
589 extract_r1cs, extract_w_x,
590 tests::{get_test_r1cs, get_test_z},
591 },
592 Arith,
593 };
594 use crate::commitment::pedersen::Pedersen;
595 use crate::folding::nova::PreprocessorParam;
596 use crate::frontend::utils::{CubicFCircuit, CustomFCircuit, WrapperCircuit};
597 use crate::transcript::poseidon::poseidon_canonical_config;
598 use crate::FoldingScheme;
599
600 // Convert `z` to a witness-instance pair for the relaxed R1CS
601 fn prepare_relaxed_witness_instance<C: CurveGroup, CS: CommitmentScheme<C>, R: Rng>(
602 mut rng: R,
603 r1cs: &R1CS<C::ScalarField>,
604 z: &[C::ScalarField],
605 ) -> (Witness<C>, CommittedInstance<C>) {
606 let (w, x) = r1cs.split_z(z);
607
608 let (cs_pp, _) = CS::setup(&mut rng, max(w.len(), r1cs.A.n_rows)).unwrap();
609
610 let mut w = Witness::new::<false>(w, r1cs.A.n_rows, &mut rng);
611 w.E = r1cs.eval_at_z(z).unwrap();
612 let mut u = w.commit::<CS, false>(&cs_pp, x).unwrap();
613 u.u = z[0];
614
615 (w, u)
616 }
617
618 #[test]
619 fn test_relaxed_r1cs_small_gadget_handcrafted() {
620 let rng = &mut thread_rng();
621
622 let r1cs: R1CS<Fr> = get_test_r1cs();
623
624 let mut z = get_test_z(3);
625 z[0] = Fr::rand(rng); // Randomize `z[0]` (i.e. `u.u`) to test the relaxed R1CS
626 let (w, u) = prepare_relaxed_witness_instance::<_, Pedersen<Projective>, _>(rng, &r1cs, &z);
627
628 let cs = ConstraintSystem::<Fr>::new_ref();
629
630 let zVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(z)).unwrap();
631 let EVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(w.E)).unwrap();
632 let uVar = FpVar::<Fr>::new_witness(cs.clone(), || Ok(u.u)).unwrap();
633 let r1csVar = R1CSVar::<Fr, Fr, FpVar<Fr>>::new_witness(cs.clone(), || Ok(r1cs)).unwrap();
634
635 RelaxedR1CSGadget::check_native(r1csVar, EVar, uVar, zVar).unwrap();
636 assert!(cs.is_satisfied().unwrap());
637 }
638
639 // gets as input a circuit that implements the ConstraintSynthesizer trait, and that has been
640 // initialized.
641 fn test_relaxed_r1cs_gadget<CS: ConstraintSynthesizer<Fr>>(circuit: CS) {
642 let rng = &mut thread_rng();
643
644 let cs = ConstraintSystem::<Fr>::new_ref();
645
646 circuit.generate_constraints(cs.clone()).unwrap();
647 cs.finalize();
648 assert!(cs.is_satisfied().unwrap());
649
650 let cs = cs.into_inner().unwrap();
651
652 let r1cs = extract_r1cs::<Fr>(&cs);
653 let (w, x) = extract_w_x::<Fr>(&cs);
654 r1cs.check_relation(&w, &x).unwrap();
655
656 let z = [vec![Fr::rand(rng)], x, w].concat();
657 let (w, u) = prepare_relaxed_witness_instance::<_, Pedersen<Projective>, _>(rng, &r1cs, &z);
658 r1cs.check_relation(&w, &u).unwrap();
659
660 // set new CS for the circuit that checks the RelaxedR1CS of our original circuit
661 let cs = ConstraintSystem::<Fr>::new_ref();
662 // prepare the inputs for our circuit
663 let zVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(z)).unwrap();
664 let EVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(w.E)).unwrap();
665 let uVar = FpVar::<Fr>::new_witness(cs.clone(), || Ok(u.u)).unwrap();
666 let r1csVar = R1CSVar::<Fr, Fr, FpVar<Fr>>::new_witness(cs.clone(), || Ok(r1cs)).unwrap();
667
668 RelaxedR1CSGadget::check_native(r1csVar, EVar, uVar, zVar).unwrap();
669 assert!(cs.is_satisfied().unwrap());
670 }
671
672 #[test]
673 fn test_relaxed_r1cs_small_gadget_arkworks() {
674 let z_i = vec![Fr::from(3_u32)];
675 let cubic_circuit = CubicFCircuit::<Fr>::new(()).unwrap();
676 let circuit = WrapperCircuit::<Fr, CubicFCircuit<Fr>> {
677 FC: cubic_circuit,
678 z_i: Some(z_i.clone()),
679 z_i1: Some(cubic_circuit.step_native(0, z_i, vec![]).unwrap()),
680 };
681
682 test_relaxed_r1cs_gadget(circuit);
683 }
684
685 struct Sha256TestCircuit<F: PrimeField> {
686 _f: PhantomData<F>,
687 pub x: Vec<u8>,
688 pub y: Vec<u8>,
689 }
690 impl<F: PrimeField> ConstraintSynthesizer<F> for Sha256TestCircuit<F> {
691 fn generate_constraints(self, cs: ConstraintSystemRef<F>) -> Result<(), SynthesisError> {
692 let x = Vec::<UInt8<F>>::new_witness(cs.clone(), || Ok(self.x))?;
693 let y = Vec::<UInt8<F>>::new_input(cs.clone(), || Ok(self.y))?;
694
695 let unitVar = UnitVar::default();
696 let comp_y = <Sha256Gadget<F> as CRHSchemeGadget<Sha256, F>>::evaluate(&unitVar, &x)?;
697 comp_y.0.enforce_equal(&y)?;
698 Ok(())
699 }
700 }
701 #[test]
702 fn test_relaxed_r1cs_medium_gadget_arkworks() {
703 let x = Fr::from(5_u32).into_bigint().to_bytes_le();
704 let y = <Sha256 as CRHScheme>::evaluate(&(), x.clone()).unwrap();
705
706 let circuit = Sha256TestCircuit::<Fr> {
707 _f: PhantomData,
708 x,
709 y,
710 };
711 test_relaxed_r1cs_gadget(circuit);
712 }
713
714 #[test]
715 fn test_relaxed_r1cs_custom_circuit() {
716 let n_constraints = 10_000;
717 let custom_circuit = CustomFCircuit::<Fr>::new(n_constraints).unwrap();
718 let z_i = vec![Fr::from(5_u32)];
719 let circuit = WrapperCircuit::<Fr, CustomFCircuit<Fr>> {
720 FC: custom_circuit,
721 z_i: Some(z_i.clone()),
722 z_i1: Some(custom_circuit.step_native(0, z_i, vec![]).unwrap()),
723 };
724 test_relaxed_r1cs_gadget(circuit);
725 }
726
727 #[test]
728 fn test_relaxed_r1cs_nonnative_circuit() {
729 let rng = &mut thread_rng();
730
731 let cs = ConstraintSystem::<Fq>::new_ref();
732 // in practice we would use CycleFoldCircuit, but is a very big circuit (when computed
733 // non-natively inside the RelaxedR1CS circuit), so in order to have a short test we use a
734 // custom circuit.
735 let custom_circuit = CustomFCircuit::<Fq>::new(10).unwrap();
736 let z_i = vec![Fq::from(5_u32)];
737 let circuit = WrapperCircuit::<Fq, CustomFCircuit<Fq>> {
738 FC: custom_circuit,
739 z_i: Some(z_i.clone()),
740 z_i1: Some(custom_circuit.step_native(0, z_i, vec![]).unwrap()),
741 };
742 circuit.generate_constraints(cs.clone()).unwrap();
743 cs.finalize();
744 let cs = cs.into_inner().unwrap();
745 let r1cs = extract_r1cs::<Fq>(&cs);
746 let (w, x) = extract_w_x::<Fq>(&cs);
747
748 let z = [vec![Fq::rand(rng)], x, w].concat();
749 let (w, u) =
750 prepare_relaxed_witness_instance::<_, Pedersen<Projective2>, _>(rng, &r1cs, &z);
751
752 // natively
753 let cs = ConstraintSystem::<Fq>::new_ref();
754 let zVar = Vec::<FpVar<Fq>>::new_witness(cs.clone(), || Ok(z.clone())).unwrap();
755 let EVar = Vec::<FpVar<Fq>>::new_witness(cs.clone(), || Ok(w.E.clone())).unwrap();
756 let uVar = FpVar::<Fq>::new_witness(cs.clone(), || Ok(u.u)).unwrap();
757 let r1csVar =
758 R1CSVar::<Fq, Fq, FpVar<Fq>>::new_witness(cs.clone(), || Ok(r1cs.clone())).unwrap();
759 RelaxedR1CSGadget::check_native(r1csVar, EVar, uVar, zVar).unwrap();
760
761 // non-natively
762 let cs = ConstraintSystem::<Fr>::new_ref();
763 let zVar = Vec::new_witness(cs.clone(), || Ok(z)).unwrap();
764 let EVar = Vec::new_witness(cs.clone(), || Ok(w.E)).unwrap();
765 let uVar = NonNativeUintVar::<Fr>::new_witness(cs.clone(), || Ok(u.u)).unwrap();
766 let r1csVar =
767 R1CSVar::<Fq, Fr, NonNativeUintVar<Fr>>::new_witness(cs.clone(), || Ok(r1cs)).unwrap();
768 RelaxedR1CSGadget::check_nonnative(r1csVar, EVar, uVar, zVar).unwrap();
769 }
770
771 #[test]
772 fn test_decider_eth_circuit() {
773 let mut rng = ark_std::test_rng();
774 let poseidon_config = poseidon_canonical_config::<Fr>();
775
776 let F_circuit = CubicFCircuit::<Fr>::new(()).unwrap();
777 let z_0 = vec![Fr::from(3_u32)];
778
779 type N = Nova<
780 Projective,
781 GVar,
782 Projective2,
783 GVar2,
784 CubicFCircuit<Fr>,
785 Pedersen<Projective>,
786 Pedersen<Projective2>,
787 false,
788 >;
789
790 let prep_param = PreprocessorParam::<
791 Projective,
792 Projective2,
793 CubicFCircuit<Fr>,
794 Pedersen<Projective>,
795 Pedersen<Projective2>,
796 false,
797 >::new(poseidon_config, F_circuit);
798 let nova_params = N::preprocess(&mut rng, &prep_param).unwrap();
799
800 // generate a Nova instance and do a step of it
801 let mut nova = N::init(&nova_params, F_circuit, z_0.clone()).unwrap();
802 nova.prove_step(&mut rng, vec![], None).unwrap();
803 let ivc_proof = nova.ivc_proof();
804 N::verify(nova_params.1, ivc_proof).unwrap();
805
806 // load the DeciderEthCircuit from the Nova instance
807 let decider_eth_circuit = DeciderEthCircuit::<
808 Projective,
809 GVar,
810 Projective2,
811 GVar2,
812 Pedersen<Projective>,
813 Pedersen<Projective2>,
814 >::from_nova(nova)
815 .unwrap();
816
817 let cs = ConstraintSystem::<Fr>::new_ref();
818
819 // generate the constraints and check that are satisfied by the inputs
820 decider_eth_circuit
821 .generate_constraints(cs.clone())
822 .unwrap();
823 assert!(cs.is_satisfied().unwrap());
824 }
825
826 // checks that the gadget and native implementations of the challenge computation match
827 #[test]
828 fn test_kzg_challenge_gadget() {
829 let mut rng = ark_std::test_rng();
830 let poseidon_config = poseidon_canonical_config::<Fr>();
831 let mut transcript = PoseidonSponge::<Fr>::new(&poseidon_config);
832
833 let U_i = CommittedInstance::<Projective> {
834 cmE: Projective::rand(&mut rng),
835 u: Fr::rand(&mut rng),
836 cmW: Projective::rand(&mut rng),
837 x: vec![Fr::rand(&mut rng); 1],
838 };
839
840 // compute the challenge natively
841 let (challenge_W, challenge_E) =
842 KZGChallengesGadget::<Projective>::get_challenges_native(&mut transcript, U_i.clone());
843
844 let cs = ConstraintSystem::<Fr>::new_ref();
845 let U_iVar =
846 CommittedInstanceVar::<Projective>::new_witness(cs.clone(), || Ok(U_i.clone()))
847 .unwrap();
848 let mut transcript_var = PoseidonSpongeVar::<Fr>::new(cs.clone(), &poseidon_config);
849
850 let (challenge_W_Var, challenge_E_Var) =
851 KZGChallengesGadget::<Projective>::get_challenges_gadget(&mut transcript_var, U_iVar)
852 .unwrap();
853 assert!(cs.is_satisfied().unwrap());
854
855 // check that the natively computed and in-circuit computed hashes match
856 use ark_r1cs_std::R1CSVar;
857 assert_eq!(challenge_W_Var.value().unwrap(), challenge_W);
858 assert_eq!(challenge_E_Var.value().unwrap(), challenge_E);
859 }
860
861 #[test]
862 fn test_polynomial_interpolation() {
863 let mut rng = ark_std::test_rng();
864 let n = 12;
865 let l = 1 << n;
866
867 let v: Vec<Fr> = std::iter::repeat_with(|| Fr::rand(&mut rng))
868 .take(l)
869 .collect();
870 let challenge = Fr::rand(&mut rng);
871
872 use ark_poly::Polynomial;
873 let polynomial = poly_from_vec(v.to_vec()).unwrap();
874 let eval = polynomial.evaluate(&challenge);
875
876 let cs = ConstraintSystem::<Fr>::new_ref();
877 let vVar = Vec::<FpVar<Fr>>::new_witness(cs.clone(), || Ok(v)).unwrap();
878 let challengeVar = FpVar::<Fr>::new_witness(cs.clone(), || Ok(challenge)).unwrap();
879
880 let evalVar = evaluate_gadget::<Fr>(vVar, challengeVar).unwrap();
881
882 use ark_r1cs_std::R1CSVar;
883 assert_eq!(evalVar.value().unwrap(), eval);
884 assert!(cs.is_satisfied().unwrap());
885 }
886}