raycrypt 0.3.1

Encrypt at the speed of light
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

use crate::utils::from_le_bytes;

fn quarter_round(a: usize, b: usize, c: usize, d: usize, block: &mut [u32; 16]) {
    block[a] = block[a].wrapping_add(block[b]);
    block[d] ^= block[a];
    block[d] = block[d].rotate_left(16);

    block[c] = block[c].wrapping_add(block[d]);
    block[b] ^= block[c];
    block[b] = block[b].rotate_left(12);

    block[a] = block[a].wrapping_add(block[b]);
    block[d] ^= block[a];
    block[d] = block[d].rotate_left(8);

    block[c] = block[c].wrapping_add(block[d]);
    block[b] ^= block[c];
    block[b] = block[b].rotate_left(7);
}

fn double_round(mut block: [u32; 16]) -> [u32; 16] {
    quarter_round(0, 4, 8, 12, &mut block);
    quarter_round(1, 5, 9, 13, &mut block);
    quarter_round(2, 6, 10, 14, &mut block);
    quarter_round(3, 7, 11, 15, &mut block);

    quarter_round(0, 5, 10, 15, &mut block);
    quarter_round(1, 6, 11, 12, &mut block);
    quarter_round(2, 7, 8, 13, &mut block);
    quarter_round(3, 4, 9, 14, &mut block);

    block
}

pub struct ChaCha20 {
    key: Vec<u8>,
}

impl ChaCha20 {
    pub fn new(key: &[u8]) -> ChaCha20 {
        ChaCha20 { key: key.to_vec() }
    }

    pub fn keystream(&self, nonce: &[u8], counter: u32) -> [u8; 64] {
        let mut state = [
            0x61707865,
            0x3320646e,
            0x79622d32,
            0x6b206574,
            from_le_bytes(&self.key[0..4]),
            from_le_bytes(&self.key[4..8]),
            from_le_bytes(&self.key[8..12]),
            from_le_bytes(&self.key[12..16]),
            from_le_bytes(&self.key[16..20]),
            from_le_bytes(&self.key[20..24]),
            from_le_bytes(&self.key[24..28]),
            from_le_bytes(&self.key[28..]),
            counter,
            from_le_bytes(&nonce[4..8]),
            from_le_bytes(&nonce[8..12]),
            from_le_bytes(&nonce[12..]),
        ];

        let mut original_state = state.clone();

        for _ in 0..10 {
            state = double_round(state);
        }

        for (i, j) in state.iter_mut().zip(original_state.iter()) {
            *i += *j;
        }

        let mut result = [0u8; 64];

        for (index, chunk) in state.iter().enumerate() {
            result[index * 4..].copy_from_slice(&chunk.to_le_bytes());
        }

        result
    }

    pub fn encrypt(&self, plaintext: &[u8], nonce: &[u8]) -> Vec<u8> {
        let mut ciphertext: Vec<u8> = Vec::new();

        for block in plaintext.chunks(64) {
            let keystream = self.keystream(nonce, 1);

            for (key, chunk) in block.iter().zip(keystream) {
                ciphertext.push(chunk ^ key);
            }
        }

        ciphertext
    }
}

pub struct HChaCha20 {
    state: [u32; 12],
}

impl HChaCha20 {
    pub fn new(key: &[u8]) -> HChaCha20 {
        let state = [
            0x61707865,
            0x3320646e,
            0x79622d32,
            0x6b206574,
            from_le_bytes(&key[0..4]),
            from_le_bytes(&key[4..8]),
            from_le_bytes(&key[8..12]),
            from_le_bytes(&key[12..16]),
            from_le_bytes(&key[16..20]),
            from_le_bytes(&key[20..24]),
            from_le_bytes(&key[24..28]),
            from_le_bytes(&key[28..32]),
        ];

        HChaCha20 { state }
    }

    pub fn keystream(&self, nonce: &[u8]) -> [u8; 32] {
        let mut state = [0u32; 16];
        state[..12].copy_from_slice(&self.state);

        state[12..16].copy_from_slice(&[
            from_le_bytes(&nonce[0..4]),
            from_le_bytes(&nonce[4..8]),
            from_le_bytes(&nonce[8..12]),
            from_le_bytes(&nonce[12..16]),
        ]);

        for _ in 0..10 {
            state = double_round(state);
        }

        let mut result = [0u8; 32];

        for (result_chunk, chunk) in result
            .chunks_exact_mut(4)
            .zip(state[0..4].iter().chain(state[12..16].iter()))
        {
            result_chunk.copy_from_slice(&chunk.to_le_bytes());
        }

        result
    }
}