eml 0.9.1

Epoch Merkle Log — multi-algorithm append-only log with epoch semantics
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
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162

//! Shared test hashers for EML unit tests.
//!
//! Provides domain-separated hash implementations across three distinct
//! algorithm families (SHA-256, SHA3-256, BLAKE2b-256) for property-based
//! and unit testing.

use blake2::Blake2b;
use blake2::digest::consts::U32;
use sha2::{Digest, Sha256};
use sha3::Sha3_256;

use crate::Hasher;

/// SHA-256 hasher (32-byte digest).
#[derive(Debug)]
pub(crate) struct Sha256Hasher;

impl Hasher for Sha256Hasher {
    fn leaf(&self, data: &[u8]) -> Vec<u8> {
        let mut h = Sha256::new();
        h.update([0x00]);
        h.update(data);
        h.finalize().to_vec()
    }

    fn node(&self, left: &[u8], right: &[u8]) -> Vec<u8> {
        let mut h = Sha256::new();
        h.update([0x01]);
        h.update(left);
        h.update(right);
        h.finalize().to_vec()
    }

    fn empty(&self) -> Vec<u8> {
        Sha256::digest(b"").to_vec()
    }

    fn null(&self) -> Vec<u8> {
        Sha256::digest([0x02]).to_vec()
    }

    fn hash(&self, data: &[u8]) -> Vec<u8> {
        Sha256::digest(data).to_vec()
    }
}

/// SHA3-256 hasher (32-byte digest, Keccak-based).
#[derive(Debug)]
pub(crate) struct Sha3Hasher;

impl Hasher for Sha3Hasher {
    fn leaf(&self, data: &[u8]) -> Vec<u8> {
        let mut h = Sha3_256::new();
        h.update([0x00]);
        h.update(data);
        h.finalize().to_vec()
    }

    fn node(&self, left: &[u8], right: &[u8]) -> Vec<u8> {
        let mut h = Sha3_256::new();
        h.update([0x01]);
        h.update(left);
        h.update(right);
        h.finalize().to_vec()
    }

    fn empty(&self) -> Vec<u8> {
        Sha3_256::digest(b"").to_vec()
    }

    fn null(&self) -> Vec<u8> {
        Sha3_256::digest([0x02]).to_vec()
    }

    fn hash(&self, data: &[u8]) -> Vec<u8> {
        Sha3_256::digest(data).to_vec()
    }
}

/// BLAKE2b-256 hasher (32-byte digest).
#[derive(Debug)]
pub(crate) struct Blake2bHasher;

impl Hasher for Blake2bHasher {
    fn leaf(&self, data: &[u8]) -> Vec<u8> {
        let mut h = Blake2b::<U32>::new();
        Digest::update(&mut h, [0x00]);
        Digest::update(&mut h, data);
        h.finalize().to_vec()
    }

    fn node(&self, left: &[u8], right: &[u8]) -> Vec<u8> {
        let mut h = Blake2b::<U32>::new();
        Digest::update(&mut h, [0x01]);
        Digest::update(&mut h, left);
        Digest::update(&mut h, right);
        h.finalize().to_vec()
    }

    fn empty(&self) -> Vec<u8> {
        <Blake2b<U32> as Digest>::digest(b"").to_vec()
    }

    fn null(&self) -> Vec<u8> {
        <Blake2b<U32> as Digest>::digest([0x02]).to_vec()
    }

    fn hash(&self, data: &[u8]) -> Vec<u8> {
        <Blake2b<U32> as Digest>::digest(data).to_vec()
    }
}

/// Second hasher for multi-algorithm tests (uses a different prefix to
/// produce distinct outputs — simulates SHA-384 without importing it).
#[derive(Debug)]
pub(crate) struct AltHasher;

impl Hasher for AltHasher {
    fn leaf(&self, data: &[u8]) -> Vec<u8> {
        let mut h = Sha256::new();
        h.update([0x00, 0xFF]); // extra byte distinguishes from Sha256Hasher
        h.update(data);
        h.finalize().to_vec()
    }

    fn node(&self, left: &[u8], right: &[u8]) -> Vec<u8> {
        let mut h = Sha256::new();
        h.update([0x01, 0xFF]);
        h.update(left);
        h.update(right);
        h.finalize().to_vec()
    }

    fn empty(&self) -> Vec<u8> {
        let mut h = Sha256::new();
        h.update([0xFF]);
        h.finalize().to_vec()
    }

    fn null(&self) -> Vec<u8> {
        let mut h = Sha256::new();
        h.update([0x02, 0xFF]);
        h.finalize().to_vec()
    }

    fn hash(&self, data: &[u8]) -> Vec<u8> {
        let mut h = Sha256::new();
        h.update([0xFF]);
        h.update(data);
        h.finalize().to_vec()
    }
}

/// Three-way hasher dispatch by algorithm ID: 0→SHA-256, 1→SHA3-256, 2→BLAKE2b.
pub(crate) fn new_hasher_for(alg_id: u64) -> Box<dyn Hasher> {
    match alg_id % 3 {
        0 => Box::new(Sha256Hasher),
        1 => Box::new(Sha3Hasher),
        2 => Box::new(Blake2bHasher),
        _ => unreachable!(),
    }
}