1use crate::{
  2    crh::{
  3        pedersen::{PedersenCRH, PedersenParameters, PedersenWindow},
  4        FixedLengthCRHGadget,
  5    },
  6    Vec,
  7};
  8use algebra_core::{Field, Group};
  9use r1cs_core::{ConstraintSystem, SynthesisError};
 10use r1cs_std::prelude::*;
 11
 12use core::{borrow::Borrow, marker::PhantomData};
 13
 14#[derive(Derivative)]
 15#[derivative(Clone(
 16    bound = "G: Group, W: PedersenWindow, ConstraintF: Field, GG: GroupGadget<G, ConstraintF>"
 17))]
 18pub struct PedersenCRHGadgetParameters<
 19    G: Group,
 20    W: PedersenWindow,
 21    ConstraintF: Field,
 22    GG: GroupGadget<G, ConstraintF>,
 23> {
 24    params: PedersenParameters<G>,
 25    _group_g: PhantomData<GG>,
 26    _engine: PhantomData<ConstraintF>,
 27    _window: PhantomData<W>,
 28}
 29
 30pub struct PedersenCRHGadget<G: Group, ConstraintF: Field, GG: GroupGadget<G, ConstraintF>> {
 31    #[doc(hideen)]
 32    _group: PhantomData<*const G>,
 33    #[doc(hideen)]
 34    _group_gadget: PhantomData<*const GG>,
 35    #[doc(hideen)]
 36    _engine: PhantomData<ConstraintF>,
 37}
 38
 39impl<ConstraintF, G, GG, W> FixedLengthCRHGadget<PedersenCRH<G, W>, ConstraintF>
 40    for PedersenCRHGadget<G, ConstraintF, GG>
 41where
 42    ConstraintF: Field,
 43    G: Group,
 44    GG: GroupGadget<G, ConstraintF>,
 45    W: PedersenWindow,
 46{
 47    type OutputGadget = GG;
 48    type ParametersGadget = PedersenCRHGadgetParameters<G, W, ConstraintF, GG>;
 49
 50    fn check_evaluation_gadget<CS: ConstraintSystem<ConstraintF>>(
 51        cs: CS,
 52        parameters: &Self::ParametersGadget,
 53        input: &[UInt8],
 54    ) -> Result<Self::OutputGadget, SynthesisError> {
 55        let mut padded_input = input.to_vec();
 56        // Pad the input if it is not the current length.
 57        if input.len() * 8 < W::WINDOW_SIZE * W::NUM_WINDOWS {
 58            let current_length = input.len();
 59            for _ in current_length..(W::WINDOW_SIZE * W::NUM_WINDOWS / 8) {
 60                padded_input.push(UInt8::constant(0u8));
 61            }
 62        }
 63        assert_eq!(padded_input.len() * 8, W::WINDOW_SIZE * W::NUM_WINDOWS);
 64        assert_eq!(parameters.params.generators.len(), W::NUM_WINDOWS);
 65
 66        // Allocate new variable for the result.
 67        let input_in_bits: Vec<_> = padded_input
 68            .iter()
 69            .flat_map(|byte| byte.into_bits_le())
 70            .collect();
 71        let input_in_bits = input_in_bits.chunks(W::WINDOW_SIZE);
 72        let result =
 73            GG::precomputed_base_multiscalar_mul(cs, &parameters.params.generators, input_in_bits)?;
 74
 75        Ok(result)
 76    }
 77}
 78
 79impl<G: Group, W: PedersenWindow, ConstraintF: Field, GG: GroupGadget<G, ConstraintF>>
 80    AllocGadget<PedersenParameters<G>, ConstraintF>
 81    for PedersenCRHGadgetParameters<G, W, ConstraintF, GG>
 82{
 83    fn alloc<F, T, CS: ConstraintSystem<ConstraintF>>(
 84        _cs: CS,
 85        value_gen: F,
 86    ) -> Result<Self, SynthesisError>
 87    where
 88        F: FnOnce() -> Result<T, SynthesisError>,
 89        T: Borrow<PedersenParameters<G>>,
 90    {
 91        let params = value_gen()?.borrow().clone();
 92        Ok(PedersenCRHGadgetParameters {
 93            params,
 94            _group_g: PhantomData,
 95            _engine: PhantomData,
 96            _window: PhantomData,
 97        })
 98    }
 99
100    fn alloc_input<F, T, CS: ConstraintSystem<ConstraintF>>(
101        _cs: CS,
102        value_gen: F,
103    ) -> Result<Self, SynthesisError>
104    where
105        F: FnOnce() -> Result<T, SynthesisError>,
106        T: Borrow<PedersenParameters<G>>,
107    {
108        let params = value_gen()?.borrow().clone();
109        Ok(PedersenCRHGadgetParameters {
110            params,
111            _group_g: PhantomData,
112            _engine: PhantomData,
113            _window: PhantomData,
114        })
115    }
116}
117
118#[cfg(test)]
119mod test {
120    use crate::crh::{
121        pedersen::{constraints::PedersenCRHGadget, PedersenCRH, PedersenWindow},
122        FixedLengthCRH, FixedLengthCRHGadget,
123    };
124    use algebra::{
125        jubjub::{Fq as Fr, JubJubProjective as JubJub},
126        test_rng, ProjectiveCurve,
127    };
128    use r1cs_core::ConstraintSystem;
129    use r1cs_std::{
130        jubjub::JubJubGadget, prelude::*, test_constraint_system::TestConstraintSystem,
131    };
132    use rand::Rng;
133
134    type TestCRH = PedersenCRH<JubJub, Window>;
135    type TestCRHGadget = PedersenCRHGadget<JubJub, Fr, JubJubGadget>;
136
137    #[derive(Clone, PartialEq, Eq, Hash)]
138    pub(super) struct Window;
139
140    impl PedersenWindow for Window {
141        const WINDOW_SIZE: usize = 128;
142        const NUM_WINDOWS: usize = 8;
143    }
144
145    fn generate_input<CS: ConstraintSystem<Fr>, R: Rng>(
146        mut cs: CS,
147        rng: &mut R,
148    ) -> ([u8; 128], Vec<UInt8>) {
149        let mut input = [1u8; 128];
150        rng.fill_bytes(&mut input);
151
152        let mut input_bytes = vec![];
153        for (byte_i, input_byte) in input.iter().enumerate() {
154            let cs = cs.ns(|| format!("input_byte_gadget_{}", byte_i));
155            input_bytes.push(UInt8::alloc(cs, || Ok(*input_byte)).unwrap());
156        }
157        (input, input_bytes)
158    }
159
160    #[test]
161    fn crh_primitive_gadget_test() {
162        let rng = &mut test_rng();
163        let mut cs = TestConstraintSystem::<Fr>::new();
164
165        let (input, input_bytes) = generate_input(&mut cs, rng);
166        println!("number of constraints for input: {}", cs.num_constraints());
167
168        let parameters = TestCRH::setup(rng).unwrap();
169        let primitive_result = TestCRH::evaluate(&parameters, &input).unwrap();
170
171        let gadget_parameters =
172            <TestCRHGadget as FixedLengthCRHGadget<TestCRH, Fr>>::ParametersGadget::alloc(
173                &mut cs.ns(|| "gadget_parameters"),
174                || Ok(&parameters),
175            )
176            .unwrap();
177        println!(
178            "number of constraints for input + params: {}",
179            cs.num_constraints()
180        );
181
182        let gadget_result =
183            <TestCRHGadget as FixedLengthCRHGadget<TestCRH, Fr>>::check_evaluation_gadget(
184                &mut cs.ns(|| "gadget_evaluation"),
185                &gadget_parameters,
186                &input_bytes,
187            )
188            .unwrap();
189
190        println!("number of constraints total: {}", cs.num_constraints());
191
192        let primitive_result = primitive_result.into_affine();
193        assert_eq!(primitive_result.x, gadget_result.x.value.unwrap());
194        assert_eq!(primitive_result.y, gadget_result.y.value.unwrap());
195        assert!(cs.is_satisfied());
196    }
197}