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/* arcfour.c --- The arcfour stream cipher
* Copyright (C) 2000-2003, 2005-2006, 2009-2011 Free Software Foundation, Inc.
*
* This file 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, or (at your
* option) any later version.
*
* This file 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this file; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
*/
/* Code from Libgcrypt adapted for gnulib by Simon Josefsson. */
/*
* For a description of the algorithm, see:
* Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
* ISBN 0-471-11709-9. Pages 397 ff.
*/
#include <config.h>
#include "arcfour.h"
void
arcfour_stream (arcfour_context * context, const char *inbuf, char *outbuf,
size_t length)
{
uint8_t i = context->idx_i;
uint8_t j = context->idx_j;
char *sbox = context->sbox;
for (; length > 0; length--)
{
char t;
i++;
j += sbox[i];
t = sbox[i];
sbox[i] = sbox[j];
sbox[j] = t;
*outbuf++ = (*inbuf++
^ sbox[(0U + sbox[i] + sbox[j]) % ARCFOUR_SBOX_SIZE]);
}
context->idx_i = i;
context->idx_j = j;
}
void
arcfour_setkey (arcfour_context * context, const char *key, size_t keylen)
{
size_t i, j, k;
char *sbox = context->sbox;
context->idx_i = context->idx_j = 0;
for (i = 0; i < ARCFOUR_SBOX_SIZE; i++)
sbox[i] = i;
for (i = j = k = 0; i < ARCFOUR_SBOX_SIZE; i++)
{
char t;
j = (j + sbox[i] + key[k]) % ARCFOUR_SBOX_SIZE;
t = sbox[i];
sbox[i] = sbox[j];
sbox[j] = t;
if (++k == keylen)
k = 0;
}
}
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