transcript_trait/
lib.rs

1use core::fmt::Debug;
2
3#[cfg(features = "merlin")]
4mod merlin;
5#[cfg(features = "merlin")]
6pub use merlin::MerlinTranscript;
7
8use digest::{typenum::type_operators::IsGreaterOrEqual, consts::U256, Digest};
9
10pub trait Transcript {
11  fn domain_separate(&mut self, label: &'static [u8]);
12  fn append_message(&mut self, label: &'static [u8], message: &[u8]);
13  fn challenge(&mut self, label: &'static [u8]) -> Vec<u8>;
14  fn rng_seed(&mut self, label: &'static [u8]) -> [u8; 32];
15}
16
17enum DigestTranscriptMember {
18  Name,
19  Domain,
20  Label,
21  Value,
22  Challenge
23}
24
25impl DigestTranscriptMember {
26  fn as_u8(&self) -> u8 {
27    match self {
28      DigestTranscriptMember::Name => 0,
29      DigestTranscriptMember::Domain => 1,
30      DigestTranscriptMember::Label => 2,
31      DigestTranscriptMember::Value => 3,
32      DigestTranscriptMember::Challenge => 4
33    }
34  }
35}
36
37#[derive(Clone, Debug)]
38pub struct DigestTranscript<D: Clone + Digest>(D) where D::OutputSize: IsGreaterOrEqual<U256>;
39
40impl<D: Clone + Digest> DigestTranscript<D> where D::OutputSize: IsGreaterOrEqual<U256> {
41  fn append(&mut self, kind: DigestTranscriptMember, value: &[u8]) {
42    self.0.update(&[kind.as_u8()]);
43    // Assumes messages don't exceed 16 exabytes
44    self.0.update(u64::try_from(value.len()).unwrap().to_le_bytes());
45    self.0.update(value);
46  }
47
48  pub fn new(name: &'static [u8]) -> Self {
49    let mut res = DigestTranscript(D::new());
50    res.append(DigestTranscriptMember::Name, name);
51    res
52  }
53}
54
55impl<D: Digest + Clone> Transcript for DigestTranscript<D>
56  where D::OutputSize: IsGreaterOrEqual<U256> {
57  fn domain_separate(&mut self, label: &[u8]) {
58    self.append(DigestTranscriptMember::Domain, label);
59  }
60
61  fn append_message(&mut self, label: &'static [u8], message: &[u8]) {
62    self.append(DigestTranscriptMember::Label, label);
63    self.append(DigestTranscriptMember::Value, message);
64  }
65
66  fn challenge(&mut self, label: &'static [u8]) -> Vec<u8> {
67    self.append(DigestTranscriptMember::Challenge, label);
68    self.0.clone().finalize().to_vec()
69  }
70
71  fn rng_seed(&mut self, label: &'static [u8]) -> [u8; 32] {
72    let mut seed = [0; 32];
73    seed.copy_from_slice(&self.challenge(label)[0 .. 32]);
74    seed
75  }
76}
77
78#[cfg(feature = "recommended")]
79pub type RecommendedTranscript = DigestTranscript<blake2::Blake2b512>;
transcript_trait/lib.rs

transcript_trait/
lib.rs
