1use crate::{CryptoError, Error};
 2use algebra_core::bytes::ToBytes;
 3use core::{fmt::Debug, hash::Hash, marker::PhantomData};
 4use rand::Rng;
 5
 6use super::{pedersen, FixedLengthCRH};
 7use algebra_core::curves::{
 8    models::{ModelParameters, TEModelParameters},
 9    twisted_edwards_extended::{GroupAffine as TEAffine, GroupProjective as TEProjective},
10    ProjectiveCurve,
11};
12
13#[cfg(feature = "r1cs")]
14pub mod constraints;
15
16pub trait InjectiveMap<C: ProjectiveCurve> {
17    type Output: ToBytes + Clone + Eq + Hash + Default + Debug;
18
19    fn injective_map(ge: &C::Affine) -> Result<Self::Output, CryptoError>;
20}
21
22pub struct TECompressor;
23
24impl<P: TEModelParameters> InjectiveMap<TEProjective<P>> for TECompressor {
25    type Output = <P as ModelParameters>::BaseField;
26
27    fn injective_map(ge: &TEAffine<P>) -> Result<Self::Output, CryptoError> {
28        debug_assert!(ge.is_in_correct_subgroup_assuming_on_curve());
29        Ok(ge.x)
30    }
31}
32
33pub struct PedersenCRHCompressor<C: ProjectiveCurve, I: InjectiveMap<C>, W: pedersen::Window> {
34    _group: PhantomData<C>,
35    _compressor: PhantomData<I>,
36    _crh: pedersen::CRH<C, W>,
37}
38
39impl<C: ProjectiveCurve, I: InjectiveMap<C>, W: pedersen::Window> FixedLengthCRH
40    for PedersenCRHCompressor<C, I, W>
41{
42    const INPUT_SIZE_BITS: usize = pedersen::CRH::<C, W>::INPUT_SIZE_BITS;
43    type Output = I::Output;
44    type Parameters = pedersen::Parameters<C>;
45
46    fn setup<R: Rng>(rng: &mut R) -> Result<Self::Parameters, Error> {
47        let time = start_timer!(|| format!("PedersenCRHCompressor::Setup"));
48        let params = pedersen::CRH::<C, W>::setup(rng);
49        end_timer!(time);
50        params
51    }
52
53    fn evaluate(parameters: &Self::Parameters, input: &[u8]) -> Result<Self::Output, Error> {
54        let eval_time = start_timer!(|| "PedersenCRHCompressor::Eval");
55        let result = I::injective_map(&pedersen::CRH::<C, W>::evaluate(parameters, input)?)?;
56        end_timer!(eval_time);
57        Ok(result)
58    }
59}