credx/presentation/
commitment.rs

1use crate::knox::short_group_sig_core::short_group_traits::ShortGroupSignatureScheme;
2use crate::presentation::{PresentationBuilder, PresentationProofs};
3use crate::statement::CommitmentStatement;
4use crate::CredxResult;
5use blsful::inner_types::{G1Projective, Scalar};
6use elliptic_curve::{group::Curve, Field};
7use merlin::Transcript;
8use rand_core::{CryptoRng, RngCore};
9use serde::{Deserialize, Serialize};
10
11/// A commitment builder
12#[derive(Debug)]
13pub(crate) struct CommitmentBuilder<'a> {
14    pub(crate) commitment: G1Projective,
15    pub(crate) statement: &'a CommitmentStatement<G1Projective>,
16    pub(crate) b: Scalar,
17    pub(crate) r: Scalar,
18}
19
20impl<S: ShortGroupSignatureScheme> PresentationBuilder<S> for CommitmentBuilder<'_> {
21    fn gen_proof(self, challenge: Scalar) -> PresentationProofs<S> {
22        let blinder_proof = self.r + challenge * self.b;
23        CommitmentProof {
24            id: self.statement.id.clone(),
25            commitment: self.commitment,
26            blinder_proof,
27        }
28        .into()
29    }
30}
31
32impl<'a> CommitmentBuilder<'a> {
33    /// Creates a commitment builder
34    pub fn commit(
35        statement: &'a CommitmentStatement<G1Projective>,
36        message: Scalar,
37        b: Scalar,
38        mut rng: impl RngCore + CryptoRng,
39        transcript: &mut Transcript,
40    ) -> CredxResult<Self> {
41        let r = Scalar::random(&mut rng);
42        let commitment = statement.message_generator * message + statement.blinder_generator * b;
43        let blind_commitment = statement.message_generator * b + statement.blinder_generator * r;
44
45        transcript.append_message(b"", statement.id.as_bytes());
46        transcript.append_message(
47            b"commitment",
48            commitment.to_affine().to_compressed().as_slice(),
49        );
50        transcript.append_message(
51            b"blind commitment",
52            blind_commitment.to_affine().to_compressed().as_slice(),
53        );
54        Ok(Self {
55            commitment,
56            statement,
57            b,
58            r,
59        })
60    }
61}
62
63/// A commitment proof
64#[derive(Clone, Debug, Deserialize, Serialize)]
65pub struct CommitmentProof {
66    /// The statement identifier
67    pub id: String,
68    /// The commitment
69    pub commitment: G1Projective,
70    /// The schnorr blinder proof
71    pub blinder_proof: Scalar,
72}
credx/presentation/commitment.rs

credx/presentation/
commitment.rs
