1use crate::group::{CompressGroupElement, DecompressGroupElement};
 2
 3use super::group::{GroupElement, VartimeMultiscalarMul, GROUP_BASEPOINT, GroupElementAffine};
 4use super::scalar::Scalar;
 5use ark_ff::PrimeField;
 6use digest::{ExtendableOutput, Input};
 7use sha3::Shake256;
 8use std::io::Read;
 9use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
10use ark_ec::{ProjectiveCurve, AffineCurve};
11
12#[derive(Debug)]
13pub struct MultiCommitGens {
14  pub n: usize,
15  pub G: Vec<GroupElement>,
16  pub h: GroupElement,
17}
18
19impl MultiCommitGens {
20  pub fn new(n: usize, label: &[u8]) -> Self {
21    let mut shake = Shake256::default();
22    shake.input(label);
23    let mut generator_encoded = Vec::new();
24    GROUP_BASEPOINT.serialize(&mut generator_encoded).unwrap();
25    shake.input(generator_encoded);
26
27    let mut reader = shake.xof_result();
28    let mut gens: Vec<GroupElement> = Vec::new();
29    let mut uniform_bytes = [0u8; 64];
30    for _ in 0..n + 1 {
31      let mut el_aff: Option<GroupElementAffine> = None;
32      while el_aff.is_some() != true {
33      reader.read_exact(&mut uniform_bytes).unwrap();
34      el_aff = GroupElementAffine::from_random_bytes(&uniform_bytes);
35    }
36    let el = el_aff.unwrap().mul_by_cofactor_to_projective();
37      gens.push(el);
38    }
39
40    MultiCommitGens {
41      n,
42      G: gens[..n].to_vec(),
43      h: gens[n],
44    }
45  }
46
47  pub fn clone(&self) -> MultiCommitGens {
48    MultiCommitGens {
49      n: self.n,
50      h: self.h,
51      G: self.G.clone(),
52    }
53  }
54
55  pub fn split_at(&self, mid: usize) -> (MultiCommitGens, MultiCommitGens) {
56    let (G1, G2) = self.G.split_at(mid);
57
58    (
59      MultiCommitGens {
60        n: G1.len(),
61        G: G1.to_vec(),
62        h: self.h,
63      },
64      MultiCommitGens {
65        n: G2.len(),
66        G: G2.to_vec(),
67        h: self.h,
68      },
69    )
70  }
71}
72
73pub trait Commitments {
74  fn commit(&self, blind: &Scalar, gens_n: &MultiCommitGens) -> GroupElement;
75}
76
77impl Commitments for Scalar {
78  fn commit(&self, blind: &Scalar, gens_n: &MultiCommitGens) -> GroupElement {
79    assert_eq!(gens_n.n, 1);
80    GroupElement::vartime_multiscalar_mul(&[*self, *blind], &[gens_n.G[0], gens_n.h])
81  }
82}
83
84impl Commitments for Vec<Scalar> {
85  fn commit(&self, blind: &Scalar, gens_n: &MultiCommitGens) -> GroupElement {
86    assert_eq!(gens_n.n, self.len());
87    GroupElement::vartime_multiscalar_mul(self, &gens_n.G) + gens_n.h.mul(blind.into_repr())
88  
89  }
90}
91
92impl Commitments for [Scalar] {
93  fn commit(&self, blind: &Scalar, gens_n: &MultiCommitGens) -> GroupElement {
94    assert_eq!(gens_n.n, self.len());
95    GroupElement::vartime_multiscalar_mul(self, &gens_n.G) + gens_n.h.mul(blind.into_repr())
96    
97  }
98}