1use super::{
  2  errors::NovaError,
  3  traits::{AppendToTranscriptTrait, CompressedGroup, Group},
  4};
  5use core::{
  6  fmt::Debug,
  7  marker::PhantomData,
  8  ops::{Add, AddAssign, Mul, MulAssign},
  9};
 10use digest::{ExtendableOutput, Input};
 11use merlin::Transcript;
 12use sha3::Shake256;
 13use std::io::Read;
 14
 15#[derive(Debug)]
 16pub struct CommitGens<G: Group> {
 17  gens: Vec<G::PreprocessedGroupElement>,
 18  _p: PhantomData<G>,
 19}
 20
 21#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 22pub struct Commitment<G: Group> {
 23  pub(crate) comm: G,
 24}
 25
 26#[derive(Clone, Debug, PartialEq, Eq)]
 27pub struct CompressedCommitment<C: CompressedGroup> {
 28  comm: C,
 29}
 30
 31impl<G: Group> CommitGens<G> {
 32  pub fn new(label: &[u8], n: usize) -> Self {
 33    let mut shake = Shake256::default();
 34    shake.input(label);
 35    let mut reader = shake.xof_result();
 36    let mut gens: Vec<G::PreprocessedGroupElement> = Vec::new();
 37    let mut uniform_bytes = [0u8; 64];
 38    for _ in 0..n {
 39      reader.read_exact(&mut uniform_bytes).unwrap();
 40      gens.push(G::from_uniform_bytes(&uniform_bytes).unwrap());
 41    }
 42
 43    CommitGens {
 44      gens,
 45      _p: PhantomData::default(),
 46    }
 47  }
 48}
 49
 50impl<G: Group> Commitment<G> {
 51  pub fn compress(&self) -> CompressedCommitment<G::CompressedGroupElement> {
 52    CompressedCommitment {
 53      comm: self.comm.compress(),
 54    }
 55  }
 56}
 57
 58impl<C: CompressedGroup> CompressedCommitment<C> {
 59  pub fn decompress(&self) -> Result<Commitment<C::GroupElement>, NovaError> {
 60    let comm = self.comm.decompress();
 61    if comm.is_none() {
 62      return Err(NovaError::DecompressionError);
 63    }
 64    Ok(Commitment {
 65      comm: comm.unwrap(),
 66    })
 67  }
 68}
 69
 70pub trait CommitTrait<G: Group> {
 71  fn commit(&self, gens: &CommitGens<G>) -> Commitment<G>;
 72}
 73
 74impl<G: Group> CommitTrait<G> for [G::Scalar] {
 75  fn commit(&self, gens: &CommitGens<G>) -> Commitment<G> {
 76    assert!(gens.gens.len() >= self.len());
 77    Commitment {
 78      comm: G::vartime_multiscalar_mul(self, &gens.gens[..self.len()]),
 79    }
 80  }
 81}
 82
 83impl<G: Group> AppendToTranscriptTrait for Commitment<G> {
 84  fn append_to_transcript(&self, label: &'static [u8], transcript: &mut Transcript) {
 85    transcript.append_message(label, self.comm.compress().as_bytes());
 86  }
 87}
 88
 89impl<C: CompressedGroup> AppendToTranscriptTrait for CompressedCommitment<C> {
 90  fn append_to_transcript(&self, label: &'static [u8], transcript: &mut Transcript) {
 91    transcript.append_message(label, self.comm.as_bytes());
 92  }
 93}
 94
 95impl<'b, G: Group> MulAssign<&'b G::Scalar> for Commitment<G> {
 96  fn mul_assign(&mut self, scalar: &'b G::Scalar) {
 97    let result = (self as &Commitment<G>).comm * scalar;
 98    *self = Commitment { comm: result };
 99  }
100}
101
102impl<'a, 'b, G: Group> Mul<&'b G::Scalar> for &'a Commitment<G> {
103  type Output = Commitment<G>;
104  fn mul(self, scalar: &'b G::Scalar) -> Commitment<G> {
105    Commitment {
106      comm: self.comm * scalar,
107    }
108  }
109}
110
111impl<G: Group> Mul<G::Scalar> for Commitment<G> {
112  type Output = Commitment<G>;
113
114  fn mul(self, scalar: G::Scalar) -> Commitment<G> {
115    Commitment {
116      comm: self.comm * scalar,
117    }
118  }
119}
120
121impl<'b, G: Group> AddAssign<&'b Commitment<G>> for Commitment<G> {
122  fn add_assign(&mut self, other: &'b Commitment<G>) {
123    let result = (self as &Commitment<G>).comm + other.comm;
124    *self = Commitment { comm: result };
125  }
126}
127
128impl<'a, 'b, G: Group> Add<&'b Commitment<G>> for &'a Commitment<G> {
129  type Output = Commitment<G>;
130  fn add(self, other: &'b Commitment<G>) -> Commitment<G> {
131    Commitment {
132      comm: self.comm + other.comm,
133    }
134  }
135}
136
137macro_rules! define_add_variants {
138  (G = $g:path, LHS = $lhs:ty, RHS = $rhs:ty, Output = $out:ty) => {
139    impl<'b, G: $g> Add<&'b $rhs> for $lhs {
140      type Output = $out;
141      fn add(self, rhs: &'b $rhs) -> $out {
142        &self + rhs
143      }
144    }
145
146    impl<'a, G: $g> Add<$rhs> for &'a $lhs {
147      type Output = $out;
148      fn add(self, rhs: $rhs) -> $out {
149        self + &rhs
150      }
151    }
152
153    impl<G: $g> Add<$rhs> for $lhs {
154      type Output = $out;
155      fn add(self, rhs: $rhs) -> $out {
156        &self + &rhs
157      }
158    }
159  };
160}
161
162macro_rules! define_add_assign_variants {
163  (G = $g:path, LHS = $lhs:ty, RHS = $rhs:ty) => {
164    impl<G: $g> AddAssign<$rhs> for $lhs {
165      fn add_assign(&mut self, rhs: $rhs) {
166        *self += &rhs;
167      }
168    }
169  };
170}
171
172define_add_assign_variants!(G = Group, LHS = Commitment<G>, RHS = Commitment<G>);
173define_add_variants!(G = Group, LHS = Commitment<G>, RHS = Commitment<G>, Output = Commitment<G>);