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/*
* ChaCha20 256-bit cipher algorithm, RFC7539
*
* Copyright (C) 2015 Martin Willi
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/bitops.h>
#include <linux/cryptohash.h>
#include <asm/unaligned.h>
#include <crypto/chacha20.h>
void chacha20_block(u32 *state, u8 *stream)
{
u32 x[16];
int i;
for (i = 0; i < ARRAY_SIZE(x); i++)
x[i] = state[i];
for (i = 0; i < 20; i += 2) {
x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16);
x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16);
x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16);
x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16);
x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12);
x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12);
x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12);
x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12);
x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8);
x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8);
x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8);
x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8);
x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7);
x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7);
x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7);
x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7);
x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16);
x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16);
x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16);
x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16);
x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12);
x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12);
x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12);
x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12);
x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8);
x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8);
x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8);
x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8);
x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7);
x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7);
x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
}
for (i = 0; i < ARRAY_SIZE(x); i++)
put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);
state[12]++;
}
EXPORT_SYMBOL(chacha20_block);
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