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99 lines
2.3 KiB
C
99 lines
2.3 KiB
C
/* This code illustrates a sample implementation
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* of the Arcfour algorithm
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* Copyright (c) April 29, 1997 Kalle Kaukonen.
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* All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that this copyright
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* notice and disclaimer are retained.
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*
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* THIS SOFTWARE IS PROVIDED BY KALLE KAUKONEN AND CONTRIBUTORS ``AS
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* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KALLE
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* KAUKONEN OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "fitz.h"
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void
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fz_arc4_init(fz_arc4 *arc4, const unsigned char *key, const unsigned keylen)
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{
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unsigned int t, u;
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unsigned int keyindex;
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unsigned int stateindex;
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unsigned char *state;
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unsigned int counter;
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state = arc4->state;
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arc4->x = 0;
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arc4->y = 0;
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for (counter = 0; counter < 256; counter++)
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{
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state[counter] = counter;
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}
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keyindex = 0;
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stateindex = 0;
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for (counter = 0; counter < 256; counter++)
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{
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t = state[counter];
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stateindex = (stateindex + key[keyindex] + t) & 0xff;
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u = state[stateindex];
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state[stateindex] = t;
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state[counter] = u;
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if (++keyindex >= keylen)
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{
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keyindex = 0;
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}
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}
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}
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static unsigned char
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fz_arc4_next(fz_arc4 *arc4)
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{
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unsigned int x;
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unsigned int y;
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unsigned int sx, sy;
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unsigned char *state;
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state = arc4->state;
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x = (arc4->x + 1) & 0xff;
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sx = state[x];
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y = (sx + arc4->y) & 0xff;
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sy = state[y];
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arc4->x = x;
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arc4->y = y;
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state[y] = sx;
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state[x] = sy;
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return state[(sx + sy) & 0xff];
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}
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void
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fz_arc4_encrypt(fz_arc4 *arc4, unsigned char *dest, const unsigned char *src, const unsigned len)
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{
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unsigned int i;
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for (i = 0; i < len; i++)
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{
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unsigned char x;
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x = fz_arc4_next(arc4);
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dest[i] = src[i] ^ x;
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}
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}
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