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// Copyright 2012 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 salsa
const rounds = 20
// core applies the Salsa20 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, c *[16]byte) {
j0 := uint32(c[0]) | uint32(c[1])<<8 | uint32(c[2])<<16 | uint32(c[3])<<24
j1 := uint32(k[0]) | uint32(k[1])<<8 | uint32(k[2])<<16 | uint32(k[3])<<24
j2 := uint32(k[4]) | uint32(k[5])<<8 | uint32(k[6])<<16 | uint32(k[7])<<24
j3 := uint32(k[8]) | uint32(k[9])<<8 | uint32(k[10])<<16 | uint32(k[11])<<24
j4 := uint32(k[12]) | uint32(k[13])<<8 | uint32(k[14])<<16 | uint32(k[15])<<24
j5 := uint32(c[4]) | uint32(c[5])<<8 | uint32(c[6])<<16 | uint32(c[7])<<24
j6 := uint32(in[0]) | uint32(in[1])<<8 | uint32(in[2])<<16 | uint32(in[3])<<24
j7 := uint32(in[4]) | uint32(in[5])<<8 | uint32(in[6])<<16 | uint32(in[7])<<24
j8 := uint32(in[8]) | uint32(in[9])<<8 | uint32(in[10])<<16 | uint32(in[11])<<24
j9 := uint32(in[12]) | uint32(in[13])<<8 | uint32(in[14])<<16 | uint32(in[15])<<24
j10 := uint32(c[8]) | uint32(c[9])<<8 | uint32(c[10])<<16 | uint32(c[11])<<24
j11 := uint32(k[16]) | uint32(k[17])<<8 | uint32(k[18])<<16 | uint32(k[19])<<24
j12 := uint32(k[20]) | uint32(k[21])<<8 | uint32(k[22])<<16 | uint32(k[23])<<24
j13 := uint32(k[24]) | uint32(k[25])<<8 | uint32(k[26])<<16 | uint32(k[27])<<24
j14 := uint32(k[28]) | uint32(k[29])<<8 | uint32(k[30])<<16 | uint32(k[31])<<24
j15 := uint32(c[12]) | uint32(c[13])<<8 | uint32(c[14])<<16 | uint32(c[15])<<24
x0, x1, x2, x3, x4, x5, x6, x7, x8 := j0, j1, j2, j3, j4, j5, j6, j7, j8
x9, x10, x11, x12, x13, x14, x15 := j9, j10, j11, j12, j13, j14, j15
for i := 0; i < rounds; i += 2 {
u := x0 + x12
x4 ^= u<<7 | u>>(32-7)
u = x4 + x0
x8 ^= u<<9 | u>>(32-9)
u = x8 + x4
x12 ^= u<<13 | u>>(32-13)
u = x12 + x8
x0 ^= u<<18 | u>>(32-18)
u = x5 + x1
x9 ^= u<<7 | u>>(32-7)
u = x9 + x5
x13 ^= u<<9 | u>>(32-9)
u = x13 + x9
x1 ^= u<<13 | u>>(32-13)
u = x1 + x13
x5 ^= u<<18 | u>>(32-18)
u = x10 + x6
x14 ^= u<<7 | u>>(32-7)
u = x14 + x10
x2 ^= u<<9 | u>>(32-9)
u = x2 + x14
x6 ^= u<<13 | u>>(32-13)
u = x6 + x2
x10 ^= u<<18 | u>>(32-18)
u = x15 + x11
x3 ^= u<<7 | u>>(32-7)
u = x3 + x15
x7 ^= u<<9 | u>>(32-9)
u = x7 + x3
x11 ^= u<<13 | u>>(32-13)
u = x11 + x7
x15 ^= u<<18 | u>>(32-18)
u = x0 + x3
x1 ^= u<<7 | u>>(32-7)
u = x1 + x0
x2 ^= u<<9 | u>>(32-9)
u = x2 + x1
x3 ^= u<<13 | u>>(32-13)
u = x3 + x2
x0 ^= u<<18 | u>>(32-18)
u = x5 + x4
x6 ^= u<<7 | u>>(32-7)
u = x6 + x5
x7 ^= u<<9 | u>>(32-9)
u = x7 + x6
x4 ^= u<<13 | u>>(32-13)
u = x4 + x7
x5 ^= u<<18 | u>>(32-18)
u = x10 + x9
x11 ^= u<<7 | u>>(32-7)
u = x11 + x10
x8 ^= u<<9 | u>>(32-9)
u = x8 + x11
x9 ^= u<<13 | u>>(32-13)
u = x9 + x8
x10 ^= u<<18 | u>>(32-18)
u = x15 + x14
x12 ^= u<<7 | u>>(32-7)
u = x12 + x15
x13 ^= u<<9 | u>>(32-9)
u = x13 + x12
x14 ^= u<<13 | u>>(32-13)
u = x14 + x13
x15 ^= u<<18 | u>>(32-18)
}
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
out[0] = byte(x0)
out[1] = byte(x0 >> 8)
out[2] = byte(x0 >> 16)
out[3] = byte(x0 >> 24)
out[4] = byte(x1)
out[5] = byte(x1 >> 8)
out[6] = byte(x1 >> 16)
out[7] = byte(x1 >> 24)
out[8] = byte(x2)
out[9] = byte(x2 >> 8)
out[10] = byte(x2 >> 16)
out[11] = byte(x2 >> 24)
out[12] = byte(x3)
out[13] = byte(x3 >> 8)
out[14] = byte(x3 >> 16)
out[15] = byte(x3 >> 24)
out[16] = byte(x4)
out[17] = byte(x4 >> 8)
out[18] = byte(x4 >> 16)
out[19] = byte(x4 >> 24)
out[20] = byte(x5)
out[21] = byte(x5 >> 8)
out[22] = byte(x5 >> 16)
out[23] = byte(x5 >> 24)
out[24] = byte(x6)
out[25] = byte(x6 >> 8)
out[26] = byte(x6 >> 16)
out[27] = byte(x6 >> 24)
out[28] = byte(x7)
out[29] = byte(x7 >> 8)
out[30] = byte(x7 >> 16)
out[31] = byte(x7 >> 24)
out[32] = byte(x8)
out[33] = byte(x8 >> 8)
out[34] = byte(x8 >> 16)
out[35] = byte(x8 >> 24)
out[36] = byte(x9)
out[37] = byte(x9 >> 8)
out[38] = byte(x9 >> 16)
out[39] = byte(x9 >> 24)
out[40] = byte(x10)
out[41] = byte(x10 >> 8)
out[42] = byte(x10 >> 16)
out[43] = byte(x10 >> 24)
out[44] = byte(x11)
out[45] = byte(x11 >> 8)
out[46] = byte(x11 >> 16)
out[47] = byte(x11 >> 24)
out[48] = byte(x12)
out[49] = byte(x12 >> 8)
out[50] = byte(x12 >> 16)
out[51] = byte(x12 >> 24)
out[52] = byte(x13)
out[53] = byte(x13 >> 8)
out[54] = byte(x13 >> 16)
out[55] = byte(x13 >> 24)
out[56] = byte(x14)
out[57] = byte(x14 >> 8)
out[58] = byte(x14 >> 16)
out[59] = byte(x14 >> 24)
out[60] = byte(x15)
out[61] = byte(x15 >> 8)
out[62] = byte(x15 >> 16)
out[63] = byte(x15 >> 24)
}
// genericXORKeyStream is the generic implementation of XORKeyStream to be used
// when no assembly implementation is available.
func genericXORKeyStream(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, &Sigma)
for i, x := range block {
out[i] = in[i] ^ x
}
u := uint32(1)
for i := 8; i < 16; 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, &Sigma)
for i, v := range in {
out[i] = v ^ block[i]
}
}
}
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