/usr/share/gocode/src/golang.org/x/crypto/chacha20poly1305/internal/chacha20/chacha_generic.go is in golang-golang-x-crypto-dev 1:0.0~git20170407.0.55a552f+REALLY.0.0~git20161012.0.5f31782-1.
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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 | // Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package ChaCha20 implements the core ChaCha20 function as specified in https://tools.ietf.org/html/rfc7539#section-2.3.
package chacha20
import "encoding/binary"
const rounds = 20
// core applies the ChaCha20 core function to 16-byte input in, 32-byte key k,
// and 16-byte constant c, and puts the result into 64-byte array out.
func core(out *[64]byte, in *[16]byte, k *[32]byte) {
j0 := uint32(0x61707865)
j1 := uint32(0x3320646e)
j2 := uint32(0x79622d32)
j3 := uint32(0x6b206574)
j4 := binary.LittleEndian.Uint32(k[0:4])
j5 := binary.LittleEndian.Uint32(k[4:8])
j6 := binary.LittleEndian.Uint32(k[8:12])
j7 := binary.LittleEndian.Uint32(k[12:16])
j8 := binary.LittleEndian.Uint32(k[16:20])
j9 := binary.LittleEndian.Uint32(k[20:24])
j10 := binary.LittleEndian.Uint32(k[24:28])
j11 := binary.LittleEndian.Uint32(k[28:32])
j12 := binary.LittleEndian.Uint32(in[0:4])
j13 := binary.LittleEndian.Uint32(in[4:8])
j14 := binary.LittleEndian.Uint32(in[8:12])
j15 := binary.LittleEndian.Uint32(in[12:16])
x0, x1, x2, x3, x4, x5, x6, x7 := j0, j1, j2, j3, j4, j5, j6, j7
x8, x9, x10, x11, x12, x13, x14, x15 := j8, j9, j10, j11, j12, j13, j14, j15
for i := 0; i < rounds; i += 2 {
x0 += x4
x12 ^= x0
x12 = (x12 << 16) | (x12 >> (16))
x8 += x12
x4 ^= x8
x4 = (x4 << 12) | (x4 >> (20))
x0 += x4
x12 ^= x0
x12 = (x12 << 8) | (x12 >> (24))
x8 += x12
x4 ^= x8
x4 = (x4 << 7) | (x4 >> (25))
x1 += x5
x13 ^= x1
x13 = (x13 << 16) | (x13 >> 16)
x9 += x13
x5 ^= x9
x5 = (x5 << 12) | (x5 >> 20)
x1 += x5
x13 ^= x1
x13 = (x13 << 8) | (x13 >> 24)
x9 += x13
x5 ^= x9
x5 = (x5 << 7) | (x5 >> 25)
x2 += x6
x14 ^= x2
x14 = (x14 << 16) | (x14 >> 16)
x10 += x14
x6 ^= x10
x6 = (x6 << 12) | (x6 >> 20)
x2 += x6
x14 ^= x2
x14 = (x14 << 8) | (x14 >> 24)
x10 += x14
x6 ^= x10
x6 = (x6 << 7) | (x6 >> 25)
x3 += x7
x15 ^= x3
x15 = (x15 << 16) | (x15 >> 16)
x11 += x15
x7 ^= x11
x7 = (x7 << 12) | (x7 >> 20)
x3 += x7
x15 ^= x3
x15 = (x15 << 8) | (x15 >> 24)
x11 += x15
x7 ^= x11
x7 = (x7 << 7) | (x7 >> 25)
x0 += x5
x15 ^= x0
x15 = (x15 << 16) | (x15 >> 16)
x10 += x15
x5 ^= x10
x5 = (x5 << 12) | (x5 >> 20)
x0 += x5
x15 ^= x0
x15 = (x15 << 8) | (x15 >> 24)
x10 += x15
x5 ^= x10
x5 = (x5 << 7) | (x5 >> 25)
x1 += x6
x12 ^= x1
x12 = (x12 << 16) | (x12 >> 16)
x11 += x12
x6 ^= x11
x6 = (x6 << 12) | (x6 >> 20)
x1 += x6
x12 ^= x1
x12 = (x12 << 8) | (x12 >> 24)
x11 += x12
x6 ^= x11
x6 = (x6 << 7) | (x6 >> 25)
x2 += x7
x13 ^= x2
x13 = (x13 << 16) | (x13 >> 16)
x8 += x13
x7 ^= x8
x7 = (x7 << 12) | (x7 >> 20)
x2 += x7
x13 ^= x2
x13 = (x13 << 8) | (x13 >> 24)
x8 += x13
x7 ^= x8
x7 = (x7 << 7) | (x7 >> 25)
x3 += x4
x14 ^= x3
x14 = (x14 << 16) | (x14 >> 16)
x9 += x14
x4 ^= x9
x4 = (x4 << 12) | (x4 >> 20)
x3 += x4
x14 ^= x3
x14 = (x14 << 8) | (x14 >> 24)
x9 += x14
x4 ^= x9
x4 = (x4 << 7) | (x4 >> 25)
}
x0 += j0
x1 += j1
x2 += j2
x3 += j3
x4 += j4
x5 += j5
x6 += j6
x7 += j7
x8 += j8
x9 += j9
x10 += j10
x11 += j11
x12 += j12
x13 += j13
x14 += j14
x15 += j15
binary.LittleEndian.PutUint32(out[0:4], x0)
binary.LittleEndian.PutUint32(out[4:8], x1)
binary.LittleEndian.PutUint32(out[8:12], x2)
binary.LittleEndian.PutUint32(out[12:16], x3)
binary.LittleEndian.PutUint32(out[16:20], x4)
binary.LittleEndian.PutUint32(out[20:24], x5)
binary.LittleEndian.PutUint32(out[24:28], x6)
binary.LittleEndian.PutUint32(out[28:32], x7)
binary.LittleEndian.PutUint32(out[32:36], x8)
binary.LittleEndian.PutUint32(out[36:40], x9)
binary.LittleEndian.PutUint32(out[40:44], x10)
binary.LittleEndian.PutUint32(out[44:48], x11)
binary.LittleEndian.PutUint32(out[48:52], x12)
binary.LittleEndian.PutUint32(out[52:56], x13)
binary.LittleEndian.PutUint32(out[56:60], x14)
binary.LittleEndian.PutUint32(out[60:64], x15)
}
// XORKeyStream crypts bytes from in to out using the given key and counters.
// In and out may be the same slice but otherwise should not overlap. Counter
// contains the raw ChaCha20 counter bytes (i.e. block counter followed by
// nonce).
func XORKeyStream(out, in []byte, counter *[16]byte, key *[32]byte) {
var block [64]byte
var counterCopy [16]byte
copy(counterCopy[:], counter[:])
for len(in) >= 64 {
core(&block, &counterCopy, key)
for i, x := range block {
out[i] = in[i] ^ x
}
u := uint32(1)
for i := 0; i < 4; i++ {
u += uint32(counterCopy[i])
counterCopy[i] = byte(u)
u >>= 8
}
in = in[64:]
out = out[64:]
}
if len(in) > 0 {
core(&block, &counterCopy, key)
for i, v := range in {
out[i] = v ^ block[i]
}
}
}
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