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/* chacha.h
*
* The ChaCha stream cipher.
* Heavily based on the Salsa20 source code in Nettle.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2013 Joachim Strömbergson
* Copyright (C) 2012 Simon Josefsson
* Copyright (C) 2014 Niels Möller
*
* 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.
*/
#ifndef NETTLE_CHACHA_H_INCLUDED
#define NETTLE_CHACHA_H_INCLUDED
#include "nettle-types.h"
#ifdef __cplusplus
extern "C" {
#endif
/* Name mangling */
#define chacha_set_key nettle_chacha_set_key
#define chacha_set_nonce nettle_chacha_set_nonce
#define chacha_crypt nettle_chacha_crypt
#define _chacha_core _nettle_chacha_core
/* Currently, only 256-bit keys are supported. */
#define CHACHA_KEY_SIZE 32
#define CHACHA_BLOCK_SIZE 64
#define CHACHA_NONCE_SIZE 8
#define _CHACHA_STATE_LENGTH 16
struct chacha_ctx
{
/* Indices 0-3 holds a constant (SIGMA or TAU).
Indices 4-11 holds the key.
Indices 12-13 holds the block counter.
Indices 14-15 holds the IV:
This creates the state matrix:
C C C C
K K K K
K K K K
B B I I
*/
uint32_t state[_CHACHA_STATE_LENGTH];
};
void
chacha_set_key(struct chacha_ctx *ctx, const uint8_t *key);
void
chacha_set_nonce(struct chacha_ctx *ctx, const uint8_t *nonce);
void
chacha_crypt(struct chacha_ctx *ctx, size_t length,
uint8_t *dst, const uint8_t *src);
void
_chacha_core(uint32_t *dst, const uint32_t *src, unsigned rounds);
#ifdef __cplusplus
}
#endif
#endif /* NETTLE_CHACHA_H_INCLUDED */
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