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68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
/*
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* Copyright 2006 Mike McCormack
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*
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* based on arc4.cpp - written and placed in the public domain by Wei Dai
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but 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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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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/* http://cryptopp.sourceforge.net/docs/ref521/arc4_8cpp-source.html */
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#include "rc4.h"
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void rc4_init(RC4_CONTEXT *a4i, const unsigned char *key, unsigned int keyLen)
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{
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unsigned int keyIndex = 0, stateIndex = 0;
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unsigned int i, a;
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a4i->x = a4i->y = 0;
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for (i=0; i<256; i++)
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a4i->state[i] = i;
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for (i=0; i<256; i++)
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{
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a = a4i->state[i];
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stateIndex += key[keyIndex] + a;
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stateIndex &= 0xff;
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a4i->state[i] = a4i->state[stateIndex];
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a4i->state[stateIndex] = a;
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if (++keyIndex >= keyLen)
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keyIndex = 0;
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}
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}
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void rc4_crypt(RC4_CONTEXT *a4i, unsigned char *inoutString, unsigned int length)
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{
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unsigned char *const s=a4i->state;
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unsigned int x = a4i->x;
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unsigned int y = a4i->y;
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unsigned int a, b;
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while(length--)
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{
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x = (x+1) & 0xff;
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a = s[x];
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y = (y+a) & 0xff;
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b = s[y];
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s[x] = b;
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s[y] = a;
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*inoutString++ ^= s[(a+b) & 0xff];
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}
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a4i->x = x;
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a4i->y = y;
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}
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