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/* chacha-crypt.c
*
* The crypt function in the ChaCha stream cipher.
* Heavily based on the Salsa20 implementation in Nettle.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2014 Niels Möller
* Copyright (C) 2013 Joachim Strömbergson
* Copyright (C) 2012 Simon Josefsson
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02111-1301, USA.
*/
/* Based on:
chacha-ref.c version 2008.01.20.
D. J. Bernstein
Public domain.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <string.h>
#include "chacha.h"
#include "macros.h"
#include "memxor.h"
#define CHACHA_ROUNDS 20
void
chacha_crypt(struct chacha_ctx *ctx,
size_t length,
uint8_t *c,
const uint8_t *m)
{
if (!length)
return;
for (;;)
{
uint32_t x[_CHACHA_STATE_LENGTH];
_chacha_core (x, ctx->state, CHACHA_ROUNDS);
ctx->state[13] += (++ctx->state[12] == 0);
/* stopping at 2^70 length per nonce is user's responsibility */
if (length <= CHACHA_BLOCK_SIZE)
{
memxor3 (c, m, x, length);
return;
}
memxor3 (c, m, x, CHACHA_BLOCK_SIZE);
length -= CHACHA_BLOCK_SIZE;
c += CHACHA_BLOCK_SIZE;
m += CHACHA_BLOCK_SIZE;
}
}
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