darkcontract 0.0.5

dark credentials and contracts with multiple attributes and custom schnorr proofs
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98

use bls12_381 as bls;
use sha2::{Digest, Sha256};

pub struct ProofHasher {
    g1_datas: Vec<[u8; 48]>,
    g2_datas: Vec<[u8; 96]>,
}

impl ProofHasher {
    pub fn new() -> Self {
        Self {
            g1_datas: Vec::new(),
            g2_datas: Vec::new(),
        }
    }

    pub fn add_g1(&mut self, point: &bls::G1Projective) {
        let point = bls::G1Affine::from(point);
        self.add_g1_affine(&point);
    }

    pub fn add_g2(&mut self, point: &bls::G2Projective) {
        let point = bls::G2Affine::from(point);
        self.add_g2_affine(&point);
    }

    pub fn add_g1_affine(&mut self, point: &bls::G1Affine) {
        let data = point.to_compressed();
        self.g1_datas.push(data);
    }

    pub fn add_g2_affine(&mut self, point: &bls::G2Affine) {
        let data = point.to_compressed();
        self.g2_datas.push(data);
    }

    pub fn finish(&self) -> bls::Scalar {
        for i in 0u32.. {
            let mut hasher = Sha256::new();

            let i_data = i.to_le_bytes();
            hasher.input(&i_data);

            for data in &self.g1_datas {
                hasher.input(&data[0..32]);
                hasher.input(&data[32..]);
            }
            for data in &self.g2_datas {
                hasher.input(&data[0..32]);
                hasher.input(&data[32..64]);
                hasher.input(&data[64..]);
            }
            let hash_result = hasher.result();

            // TODO: how can I fix this? Why not &hash_result[0...32]??
            let mut hash_data = [0u8; 32];
            hash_data.copy_from_slice(hash_result.as_slice());

            let challenge = bls::Scalar::from_bytes(&hash_data);
            if challenge.is_some().unwrap_u8() == 1 {
                return challenge.unwrap();
            }
        }
        unreachable!();
    }
}

pub trait ProofBuilder {
    fn finish(&self, challenge: &bls::Scalar);
}

pub trait ProofCommitments {
    fn commit(&self, hasher: &mut ProofHasher);
}

pub struct ProofAssembly<'a> {
    commits: Vec<Box<dyn ProofCommitments + 'a>>,
}

impl<'a> ProofAssembly<'a> {
    pub fn new() -> Self {
        Self {
            commits: Vec::new(),
        }
    }

    pub fn add(&mut self, commit: Box<dyn ProofCommitments + 'a>) {
        self.commits.push(commit);
    }

    pub fn compute_challenge(&self) -> bls::Scalar {
        let mut hasher = ProofHasher::new();
        for commit in &self.commits {
            commit.commit(&mut hasher);
        }
        hasher.finish()
    }
}