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/* salsa20-set-key.c
*
* The Salsa20 stream cipher.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2012 Simon Josefsson, 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.
*/
/* Based on:
salsa20-ref.c version 20051118
D. J. Bernstein
Public domain.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include "salsa20.h"
#include "macros.h"
void
salsa20_set_key(struct salsa20_ctx *ctx,
size_t length, const uint8_t *key)
{
static const uint32_t sigma[4] = {
/* "expand 32-byte k" */
0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
};
static const uint32_t tau[4] = {
/* "expand 16-byte k" */
0x61707865, 0x3120646e, 0x79622d36, 0x6b206574
};
const uint32_t *constants;
assert (length == SALSA20_MIN_KEY_SIZE || length == SALSA20_MAX_KEY_SIZE);
ctx->input[1] = LE_READ_UINT32(key + 0);
ctx->input[2] = LE_READ_UINT32(key + 4);
ctx->input[3] = LE_READ_UINT32(key + 8);
ctx->input[4] = LE_READ_UINT32(key + 12);
if (length == SALSA20_MAX_KEY_SIZE) { /* recommended */
ctx->input[11] = LE_READ_UINT32(key + 16);
ctx->input[12] = LE_READ_UINT32(key + 20);
ctx->input[13] = LE_READ_UINT32(key + 24);
ctx->input[14] = LE_READ_UINT32(key + 28);
constants = sigma;
} else { /* kbits == 128 */
ctx->input[11] = ctx->input[1];
ctx->input[12] = ctx->input[2];
ctx->input[13] = ctx->input[3];
ctx->input[14] = ctx->input[4];
constants = tau;
}
ctx->input[0] = constants[0];
ctx->input[5] = constants[1];
ctx->input[10] = constants[2];
ctx->input[15] = constants[3];
}
void
salsa20_set_iv(struct salsa20_ctx *ctx, const uint8_t *iv)
{
ctx->input[6] = LE_READ_UINT32(iv + 0);
ctx->input[7] = LE_READ_UINT32(iv + 4);
ctx->input[8] = 0;
ctx->input[9] = 0;
}
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