rscrypto 0.1.1

Pure Rust cryptography, hardware-accelerated: BLAKE3, SHA-2/3, AES-GCM, ChaCha20-Poly1305, Ed25519, X25519, HMAC, HKDF, Argon2, CRC. no_std, WASM, ten CPU architectures.
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
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181

use core::arch::aarch64::{
  uint32x4_t, vaddq_u32, vdupq_n_u32, veorq_u32, vld1q_u32, vorrq_u32, vshlq_n_u32, vshrq_n_u32, vst1q_u32,
};

use super::{BLOCK_SIZE, KEY_SIZE, NONCE_SIZE, load_u32_le, xor_keystream_portable};

const BLOCKS_PER_BATCH: usize = 4;

#[inline]
pub(super) fn xor_keystream(key: &[u8; KEY_SIZE], initial_counter: u32, nonce: &[u8; NONCE_SIZE], buffer: &mut [u8]) {
  // SAFETY: Backend selection guarantees NEON is available before this wrapper is chosen.
  unsafe { xor_keystream_impl(key, initial_counter, nonce, buffer) }
}

#[target_feature(enable = "neon")]
unsafe fn xor_keystream_impl(key: &[u8; KEY_SIZE], initial_counter: u32, nonce: &[u8; NONCE_SIZE], buffer: &mut [u8]) {
  let mut counter = initial_counter;
  let mut batches = buffer.chunks_exact_mut(BLOCK_SIZE * BLOCKS_PER_BATCH);
  for chunk in &mut batches {
    debug_assert!(counter.checked_add((BLOCKS_PER_BATCH - 1) as u32).is_some());

    let mut x0 = vdupq_n_u32(0x6170_7865);
    let mut x1 = vdupq_n_u32(0x3320_646e);
    let mut x2 = vdupq_n_u32(0x7962_2d32);
    let mut x3 = vdupq_n_u32(0x6b20_6574);
    let mut x4 = vdupq_n_u32(load_u32_le(&key[0..4]));
    let mut x5 = vdupq_n_u32(load_u32_le(&key[4..8]));
    let mut x6 = vdupq_n_u32(load_u32_le(&key[8..12]));
    let mut x7 = vdupq_n_u32(load_u32_le(&key[12..16]));
    let mut x8 = vdupq_n_u32(load_u32_le(&key[16..20]));
    let mut x9 = vdupq_n_u32(load_u32_le(&key[20..24]));
    let mut x10 = vdupq_n_u32(load_u32_le(&key[24..28]));
    let mut x11 = vdupq_n_u32(load_u32_le(&key[28..32]));
    let counter_words = [
      counter,
      counter.wrapping_add(1),
      counter.wrapping_add(2),
      counter.wrapping_add(3),
    ];
    // SAFETY: `counter_words` is a properly aligned local array with four initialized `u32` lanes.
    let mut x12 = unsafe { vld1q_u32(counter_words.as_ptr()) };
    let mut x13 = vdupq_n_u32(load_u32_le(&nonce[0..4]));
    let mut x14 = vdupq_n_u32(load_u32_le(&nonce[4..8]));
    let mut x15 = vdupq_n_u32(load_u32_le(&nonce[8..12]));

    let o0 = x0;
    let o1 = x1;
    let o2 = x2;
    let o3 = x3;
    let o4 = x4;
    let o5 = x5;
    let o6 = x6;
    let o7 = x7;
    let o8 = x8;
    let o9 = x9;
    let o10 = x10;
    let o11 = x11;
    let o12 = x12;
    let o13 = x13;
    let o14 = x14;
    let o15 = x15;

    let mut round = 0usize;
    while round < 10 {
      quarter_round(&mut x0, &mut x4, &mut x8, &mut x12);
      quarter_round(&mut x1, &mut x5, &mut x9, &mut x13);
      quarter_round(&mut x2, &mut x6, &mut x10, &mut x14);
      quarter_round(&mut x3, &mut x7, &mut x11, &mut x15);

      quarter_round(&mut x0, &mut x5, &mut x10, &mut x15);
      quarter_round(&mut x1, &mut x6, &mut x11, &mut x12);
      quarter_round(&mut x2, &mut x7, &mut x8, &mut x13);
      quarter_round(&mut x3, &mut x4, &mut x9, &mut x14);

      round = round.strict_add(1);
    }

    x0 = vaddq_u32(x0, o0);
    x1 = vaddq_u32(x1, o1);
    x2 = vaddq_u32(x2, o2);
    x3 = vaddq_u32(x3, o3);
    x4 = vaddq_u32(x4, o4);
    x5 = vaddq_u32(x5, o5);
    x6 = vaddq_u32(x6, o6);
    x7 = vaddq_u32(x7, o7);
    x8 = vaddq_u32(x8, o8);
    x9 = vaddq_u32(x9, o9);
    x10 = vaddq_u32(x10, o10);
    x11 = vaddq_u32(x11, o11);
    x12 = vaddq_u32(x12, o12);
    x13 = vaddq_u32(x13, o13);
    x14 = vaddq_u32(x14, o14);
    x15 = vaddq_u32(x15, o15);

    let mut words = [[0u32; BLOCKS_PER_BATCH]; 16];
    // SAFETY: each destination is a valid four-lane `u32` array.
    unsafe {
      vst1q_u32(words[0].as_mut_ptr(), x0);
      vst1q_u32(words[1].as_mut_ptr(), x1);
      vst1q_u32(words[2].as_mut_ptr(), x2);
      vst1q_u32(words[3].as_mut_ptr(), x3);
      vst1q_u32(words[4].as_mut_ptr(), x4);
      vst1q_u32(words[5].as_mut_ptr(), x5);
      vst1q_u32(words[6].as_mut_ptr(), x6);
      vst1q_u32(words[7].as_mut_ptr(), x7);
      vst1q_u32(words[8].as_mut_ptr(), x8);
      vst1q_u32(words[9].as_mut_ptr(), x9);
      vst1q_u32(words[10].as_mut_ptr(), x10);
      vst1q_u32(words[11].as_mut_ptr(), x11);
      vst1q_u32(words[12].as_mut_ptr(), x12);
      vst1q_u32(words[13].as_mut_ptr(), x13);
      vst1q_u32(words[14].as_mut_ptr(), x14);
      vst1q_u32(words[15].as_mut_ptr(), x15);
    }

    let mut block_index = 0usize;
    while block_index < BLOCKS_PER_BATCH {
      let mut word_index = 0usize;
      while word_index < 16 {
        let offset = block_index.strict_mul(BLOCK_SIZE).strict_add(word_index.strict_mul(4));
        let keystream = words[word_index][block_index].to_le_bytes();
        chunk[offset..offset.strict_add(4)]
          .iter_mut()
          .zip(keystream)
          .for_each(|(dst, src)| *dst ^= src);
        word_index = word_index.strict_add(1);
      }
      block_index = block_index.strict_add(1);
    }

    counter = counter.wrapping_add(BLOCKS_PER_BATCH as u32);
  }

  let remainder = batches.into_remainder();
  if !remainder.is_empty() {
    xor_keystream_portable(key, counter, nonce, remainder);
  }
}

#[inline(always)]
fn quarter_round(a: &mut uint32x4_t, b: &mut uint32x4_t, c: &mut uint32x4_t, d: &mut uint32x4_t) {
  // SAFETY: this helper is only reached from the NEON-enabled backend.
  unsafe {
    *a = vaddq_u32(*a, *b);
    *d = rotl16(veorq_u32(*d, *a));
    *c = vaddq_u32(*c, *d);
    *b = rotl12(veorq_u32(*b, *c));
    *a = vaddq_u32(*a, *b);
    *d = rotl8(veorq_u32(*d, *a));
    *c = vaddq_u32(*c, *d);
    *b = rotl7(veorq_u32(*b, *c));
  }
}

#[inline(always)]
fn rotl16(value: uint32x4_t) -> uint32x4_t {
  // SAFETY: this helper is only reached from the NEON-enabled backend and only uses fixed shift
  // amounts.
  unsafe { vorrq_u32(vshlq_n_u32(value, 16), vshrq_n_u32(value, 16)) }
}

#[inline(always)]
fn rotl12(value: uint32x4_t) -> uint32x4_t {
  // SAFETY: this helper is only reached from the NEON-enabled backend and only uses fixed shift
  // amounts.
  unsafe { vorrq_u32(vshlq_n_u32(value, 12), vshrq_n_u32(value, 20)) }
}

#[inline(always)]
fn rotl8(value: uint32x4_t) -> uint32x4_t {
  // SAFETY: this helper is only reached from the NEON-enabled backend and only uses fixed shift
  // amounts.
  unsafe { vorrq_u32(vshlq_n_u32(value, 8), vshrq_n_u32(value, 24)) }
}

#[inline(always)]
fn rotl7(value: uint32x4_t) -> uint32x4_t {
  // SAFETY: this helper is only reached from the NEON-enabled backend and only uses fixed shift
  // amounts.
  unsafe { vorrq_u32(vshlq_n_u32(value, 7), vshrq_n_u32(value, 25)) }
}