1use crate::{Parameters, PublicKey, Signature};
  2
  3use ark_ec::ProjectiveCurve;
  4use ark_ed_on_bn254::{constraints::EdwardsVar, EdwardsParameters, FqParameters};
  5use ark_ff::{fields::Fp256, to_bytes, PrimeField};
  6use ark_r1cs_std::{
  7    alloc::{AllocVar, AllocationMode},
  8    bits::uint8::UInt8,
  9    boolean::Boolean,
 10    eq::EqGadget,
 11    fields::fp::FpVar,
 12    groups::GroupOpsBounds,
 13    prelude::CurveVar,
 14    ToBitsGadget,
 15};
 16use ark_relations::r1cs::{ConstraintSynthesizer, ConstraintSystemRef, Namespace, SynthesisError};
 17use ark_std::ops::Mul;
 18
 19use core::{borrow::Borrow, marker::PhantomData};
 20use derivative::Derivative;
 21
 22// hash
 23use arkworks_native_gadgets::poseidon as poseidon_native;
 24// use arkworks_r1cs_gadgets::poseidon;
 25use arkworks_r1cs_gadgets::poseidon::{FieldHasherGadget, PoseidonGadget};
 26
 27use crate::ConstraintF;
 28
 29#[derive(Derivative)]
 30#[derivative(
 31    Debug(bound = "C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>"),
 32    Clone(bound = "C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>")
 33)]
 34pub struct PublicKeyVar<C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>>
 35where
 36    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
 37{
 38    pub_key: GC,
 39    #[doc(hidden)]
 40    _group: PhantomData<*const C>,
 41}
 42
 43impl<C, GC> AllocVar<PublicKey<C>, ConstraintF<C>> for PublicKeyVar<C, GC>
 44where
 45    C: ProjectiveCurve,
 46    GC: CurveVar<C, ConstraintF<C>>,
 47    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
 48{
 49    fn new_variable<T: Borrow<PublicKey<C>>>(
 50        cs: impl Into<Namespace<ConstraintF<C>>>,
 51        f: impl FnOnce() -> Result<T, SynthesisError>,
 52        mode: AllocationMode,
 53    ) -> Result<Self, SynthesisError> {
 54        let pub_key = GC::new_variable(cs, f, mode)?;
 55        Ok(Self {
 56            pub_key,
 57            _group: PhantomData,
 58        })
 59    }
 60}
 61
 62#[derive(Derivative)]
 63#[derivative(
 64    Debug(bound = "C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>"),
 65    Clone(bound = "C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>")
 66)]
 67pub struct SignatureVar<C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>>
 68where
 69    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
 70{
 71    s: Vec<UInt8<ConstraintF<C>>>,
 72    r: GC,
 73    _curve: PhantomData<C>,
 74}
 75
 76impl<C, GC> AllocVar<Signature<C>, ConstraintF<C>> for SignatureVar<C, GC>
 77where
 78    C: ProjectiveCurve,
 79    GC: CurveVar<C, ConstraintF<C>>,
 80    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
 81{
 82    fn new_variable<T: Borrow<Signature<C>>>(
 83        cs: impl Into<Namespace<ConstraintF<C>>>,
 84        f: impl FnOnce() -> Result<T, SynthesisError>,
 85        mode: AllocationMode,
 86    ) -> Result<Self, SynthesisError> {
 87        f().and_then(|val| {
 88            let cs = cs.into();
 89            // let s = val.borrow().s;
 90            let mut s = Vec::<UInt8<ConstraintF<C>>>::new();
 91            let s_bytes = to_bytes![val.borrow().s].unwrap();
 92            #[allow(clippy::needless_range_loop)]
 93            for i in 0..s_bytes.len() {
 94                s.push(UInt8::<ConstraintF<C>>::new_variable(
 95                    cs.clone(),
 96                    || Ok(s_bytes[i]),
 97                    mode,
 98                )?);
 99            }
100
101            let r = GC::new_variable(cs, || Ok(val.borrow().r), mode)?;
102
103            Ok(Self {
104                s,
105                r,
106                _curve: PhantomData,
107            })
108        })
109    }
110}
111
112#[derive(Clone)]
113pub struct ParametersVar<C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>>
114where
115    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
116{
117    generator: GC,
118    _curve: PhantomData<C>,
119}
120
121impl<C, GC> AllocVar<Parameters<C>, ConstraintF<C>> for ParametersVar<C, GC>
122where
123    C: ProjectiveCurve,
124    GC: CurveVar<C, ConstraintF<C>>,
125    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
126{
127    fn new_variable<T: Borrow<Parameters<C>>>(
128        cs: impl Into<Namespace<ConstraintF<C>>>,
129        f: impl FnOnce() -> Result<T, SynthesisError>,
130        mode: AllocationMode,
131    ) -> Result<Self, SynthesisError> {
132        f().and_then(|val| {
133            let cs = cs.into();
134            let generator = GC::new_variable(cs, || Ok(val.borrow().generator), mode)?;
135            Ok(Self {
136                generator,
137                _curve: PhantomData,
138            })
139        })
140    }
141}
142
143pub struct BlindSigVerifyGadget<C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>>
144where
145    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
146{
147    _params: Parameters<C>, // TODO review if needed, maybe delete
148    _gc: PhantomData<GC>,
149}
150
151impl<C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>> BlindSigVerifyGadget<C, GC>
152where
153    C: ProjectiveCurve,
154    GC: CurveVar<C, ConstraintF<C>>,
155    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
156    ark_r1cs_std::groups::curves::twisted_edwards::AffineVar<
157        EdwardsParameters,
158        FpVar<Fp256<FqParameters>>,
159    >: From<GC>,
160    <C as ProjectiveCurve>::BaseField: PrimeField,
161    FpVar<<C as ProjectiveCurve>::BaseField>: Mul<FpVar<Fp256<FqParameters>>>,
162    FpVar<<C as ProjectiveCurve>::BaseField>: From<FpVar<Fp256<FqParameters>>>,
163{
164    fn verify(
165        parameters: &ParametersVar<C, GC>,
166        poseidon_hash: &PoseidonGadget<ConstraintF<C>>,
167        m: FpVar<ConstraintF<C>>,
168        s: &SignatureVar<C, GC>,
169        q: &PublicKeyVar<C, GC>,
170    ) -> Result<Boolean<ConstraintF<C>>, SynthesisError> {
171        let s_s = s.s.clone();
172
173        let sG = parameters
174            .generator
175            .scalar_mul_le(s_s.to_bits_le()?.iter())?;
176
177        // Note: in a circuit that aggregates multiple verifications, the hashing step could be
178        // done outside the signature verification, once for all 1 votes and once for all 0 votes,
179        // saving lots of constraints
180        let hm = poseidon_hash.hash(&[m])?;
181        let r = EdwardsVar::from(s.r.clone()); // WIP
182        let rx_fpvar: FpVar<ConstraintF<C>> = r.x.into();
183
184        // G * s == R + Q * (R.x * H(m))
185        let Q_rx_hm_0 = q.pub_key.scalar_mul_le(rx_fpvar.to_bits_le()?.iter())?;
186        let Q_rx_hm = Q_rx_hm_0.scalar_mul_le(hm.to_bits_le()?.iter())?;
187        let RHS = s.r.clone() + Q_rx_hm;
188
189        sG.is_eq(&RHS)
190    }
191}
192
193// example of circuit using BlindSigVerifyGadget
194#[derive(Clone)]
195pub struct BlindSigVerifyCircuit<C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>>
196where
197    <C as ProjectiveCurve>::BaseField: PrimeField,
198{
199    _group: PhantomData<*const GC>,
200    pub params: Parameters<C>,
201    pub poseidon_hash_native: poseidon_native::Poseidon<ConstraintF<C>>,
202    pub signature: Option<Signature<C>>,
203    pub pub_key: Option<PublicKey<C>>,
204    pub message: Option<ConstraintF<C>>,
205}
206
207impl<C: ProjectiveCurve, GC: CurveVar<C, ConstraintF<C>>> ConstraintSynthesizer<ConstraintF<C>>
208    for BlindSigVerifyCircuit<C, GC>
209where
210    C: ProjectiveCurve,
211    GC: CurveVar<C, ConstraintF<C>>,
212    for<'a> &'a GC: GroupOpsBounds<'a, C, GC>,
213    ark_r1cs_std::groups::curves::twisted_edwards::AffineVar<
214        EdwardsParameters,
215        FpVar<Fp256<FqParameters>>,
216    >: From<GC>,
217    <C as ProjectiveCurve>::BaseField: PrimeField,
218    FpVar<<C as ProjectiveCurve>::BaseField>: Mul<FpVar<Fp256<FqParameters>>>,
219    FpVar<<C as ProjectiveCurve>::BaseField>: From<FpVar<Fp256<FqParameters>>>,
220{
221    #[tracing::instrument(target = "r1cs", skip(self, cs))]
222    fn generate_constraints(
223        self,
224        cs: ConstraintSystemRef<ConstraintF<C>>,
225    ) -> Result<(), SynthesisError> {
226        let parameters =
227            ParametersVar::new_constant(ark_relations::ns!(cs, "parameters"), &self.params)?;
228
229        let pub_key =
230            PublicKeyVar::<C, GC>::new_input(ark_relations::ns!(cs, "public key"), || {
231                self.pub_key.ok_or(SynthesisError::AssignmentMissing)
232            })?;
233        let m = FpVar::<ConstraintF<C>>::new_input(ark_relations::ns!(cs, "message"), || {
234            self.message.ok_or(SynthesisError::AssignmentMissing)
235        })?;
236        let signature =
237            SignatureVar::<C, GC>::new_witness(ark_relations::ns!(cs, "signature"), || {
238                self.signature.ok_or(SynthesisError::AssignmentMissing)
239            })?;
240        #[allow(clippy::redundant_clone)]
241        let poseidon_hash = PoseidonGadget::<ConstraintF<C>>::from_native(
242            &mut cs.clone(),
243            self.poseidon_hash_native,
244        )
245        .unwrap();
246
247        let v = BlindSigVerifyGadget::<C, GC>::verify(
248            &parameters,
249            &poseidon_hash,
250            m,
251            &signature,
252            &pub_key,
253        )?;
254        v.enforce_equal(&Boolean::TRUE)
255    }
256}
257
258#[cfg(test)]
259mod test {
260    use super::*;
261    use crate::{poseidon_setup_params, BlindSigScheme};
262    use ark_ed_on_bn254::constraints::EdwardsVar as BabyJubJubVar;
263    use ark_ed_on_bn254::EdwardsProjective as BabyJubJub;
264
265    use arkworks_native_gadgets::poseidon;
266    use arkworks_utils::Curve;
267
268    use ark_relations::r1cs::ConstraintSystem;
269
270    type Fq = <BabyJubJub as ProjectiveCurve>::BaseField;
271    // type Fr = <BabyJubJub as ProjectiveCurve>::ScalarField;
272    type S = BlindSigScheme<BabyJubJub>;
273
274    fn generate_native_data(
275        poseidon_hash: &poseidon::Poseidon<Fq>,
276    ) -> (
277        Parameters<BabyJubJub>,
278        PublicKey<BabyJubJub>,
279        Fq,
280        Signature<BabyJubJub>,
281    ) {
282        let mut rng = ark_std::test_rng();
283        let params = S::setup();
284        let (pk, sk) = S::keygen(&params, &mut rng);
285        let (k, signer_r) = S::new_request_params(&params, &mut rng);
286        let m = Fq::from(1234);
287        let (m_blinded, u) = S::blind(&params, &mut rng, &poseidon_hash, m, signer_r).unwrap();
288        let s_blinded = S::blind_sign(sk, k, m_blinded);
289        let s = S::unblind(s_blinded, u);
290        let verified = S::verify(&params, &poseidon_hash, m, s.clone(), pk);
291        assert!(verified);
292        (params, pk, m, s)
293    }
294
295    #[test]
296    fn test_verify() {
297        let poseidon_params = poseidon_setup_params::<Fq>(Curve::Bn254, 5, 3);
298        let poseidon_hash = poseidon::Poseidon::new(poseidon_params);
299
300        // create signature using native-rust lib
301        let (params, pk, m, s) = generate_native_data(&poseidon_hash);
302
303        // use the constraint system to verify the signature
304        type SG = BlindSigVerifyGadget<BabyJubJub, BabyJubJubVar>;
305        let cs = ConstraintSystem::<Fq>::new_ref();
306
307        let params_var =
308            ParametersVar::<BabyJubJub, BabyJubJubVar>::new_constant(cs.clone(), params).unwrap();
309        let signature_var =
310            SignatureVar::<BabyJubJub, BabyJubJubVar>::new_witness(cs.clone(), || Ok(&s)).unwrap();
311        let pk_var =
312            PublicKeyVar::<BabyJubJub, BabyJubJubVar>::new_witness(cs.clone(), || Ok(&pk)).unwrap();
313        let m_var = FpVar::<Fq>::new_witness(cs.clone(), || Ok(&m)).unwrap();
314        let poseidon_hash_var =
315            PoseidonGadget::<Fq>::from_native(&mut cs.clone(), poseidon_hash).unwrap();
316
317        let valid_sig = SG::verify(
318            &params_var,
319            &poseidon_hash_var,
320            m_var,
321            &signature_var,
322            &pk_var,
323        )
324        .unwrap();
325        valid_sig.enforce_equal(&Boolean::<Fq>::TRUE).unwrap();
326        assert!(cs.is_satisfied().unwrap());
327    }
328
329    #[test]
330    fn test_constraint_system() {
331        let poseidon_params = poseidon_setup_params::<Fq>(Curve::Bn254, 5, 3);
332        let poseidon_hash = poseidon::Poseidon::new(poseidon_params);
333
334        // create signature using native-rust lib
335        let (params, pk, m, s) = generate_native_data(&poseidon_hash);
336
337        // use the constraint system to verify the signature
338        let circuit = BlindSigVerifyCircuit::<BabyJubJub, BabyJubJubVar> {
339            params,
340            poseidon_hash_native: poseidon_hash,
341            signature: Some(s),
342            pub_key: Some(pk),
343            message: Some(m),
344            _group: PhantomData,
345        };
346        let cs = ConstraintSystem::<Fq>::new_ref();
347        circuit.generate_constraints(cs.clone()).unwrap();
348        let is_satisfied = cs.is_satisfied().unwrap();
349        assert!(is_satisfied);
350        println!("num_cnstraints={:?}", cs.num_constraints());
351    }
352}