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80 lines
2.0 KiB
C
80 lines
2.0 KiB
C
/* arcfour.c --- The arcfour stream cipher
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* Copyright (C) 2000, 2001, 2002, 2003, 2005 Free Software Foundation, Inc.
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published
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* by the Free Software Foundation; either version 2, or (at your
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* option) any later version.
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*
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* This file is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this file; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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*/
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/* Code from Libgcrypt adapted for gnulib by Simon Josefsson. */
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/*
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* For a description of the algorithm, see:
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* Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
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* ISBN 0-471-11709-9. Pages 397 ff.
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*/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include "arcfour.h"
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void
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arcfour_stream (arcfour_context * context, const char *inbuf, char *outbuf,
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size_t length)
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{
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uint8_t i = context->idx_i;
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uint8_t j = context->idx_j;
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char *sbox = context->sbox;
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for (; length > 0; length--)
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{
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char t;
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i++;
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j += sbox[i];
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t = sbox[i];
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sbox[i] = sbox[j];
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sbox[j] = t;
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*outbuf++ = (*inbuf++
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^ sbox[(0U + sbox[i] + sbox[j]) % ARCFOUR_SBOX_SIZE]);
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}
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context->idx_i = i;
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context->idx_j = j;
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}
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void
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arcfour_setkey (arcfour_context * context, const char *key, size_t keylen)
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{
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size_t i, j, k;
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char *sbox = context->sbox;
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context->idx_i = context->idx_j = 0;
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for (i = 0; i < ARCFOUR_SBOX_SIZE; i++)
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sbox[i] = i;
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for (i = j = k = 0; i < ARCFOUR_SBOX_SIZE; i++)
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{
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char t;
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j = (j + sbox[i] + key[k]) % ARCFOUR_SBOX_SIZE;
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t = sbox[i];
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sbox[i] = sbox[j];
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sbox[j] = t;
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if (++k == keylen)
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k = 0;
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}
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}
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