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/*
* File: rc4.c
*
* This program 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 of the License, or
* (at your option) any later version.
*
* This program 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 program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Purpose:
*
* Functions:
*
* Revision History:
*
* Author: Kyle Hsu
*
* Date: Sep 4, 2002
*
*/
#if !defined(__RC4_H__)
#include "rc4.h"
#endif
VOID rc4_init(PRC4Ext pRC4, PBYTE pbyKey, UINT cbKey_len)
{
UINT ust1, ust2;
UINT keyindex;
UINT stateindex;
PBYTE pbyst;
UINT idx;
pbyst = pRC4->abystate;
pRC4->ux = 0;
pRC4->uy = 0;
for (idx = 0; idx < 256; idx++)
pbyst[idx] = (BYTE)idx;
keyindex = 0;
stateindex = 0;
for (idx = 0; idx < 256; idx++) {
ust1 = pbyst[idx];
stateindex = (stateindex + pbyKey[keyindex] + ust1) & 0xff;
ust2 = pbyst[stateindex];
pbyst[stateindex] = (BYTE)ust1;
pbyst[idx] = (BYTE)ust2;
if (++keyindex >= cbKey_len)
keyindex = 0;
}
}
UINT rc4_byte(PRC4Ext pRC4)
{
UINT ux;
UINT uy;
UINT ustx, usty;
PBYTE pbyst;
pbyst = pRC4->abystate;
ux = (pRC4->ux + 1) & 0xff;
ustx = pbyst[ux];
uy = (ustx + pRC4->uy) & 0xff;
usty = pbyst[uy];
pRC4->ux = ux;
pRC4->uy = uy;
pbyst[uy] = (BYTE)ustx;
pbyst[ux] = (BYTE)usty;
return pbyst[(ustx + usty) & 0xff];
}
VOID rc4_encrypt(PRC4Ext pRC4, PBYTE pbyDest,
PBYTE pbySrc, UINT cbData_len)
{
UINT ii;
for (ii = 0; ii < cbData_len; ii++)
pbyDest[ii] = (BYTE)(pbySrc[ii] ^ rc4_byte(pRC4));
}
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