rc4.c

VIA VT6656 USB linux source code.

/*
 * Copyright (c) 1996, 2003 VIA Networking Technologies, Inc.
 * All rights reserved.
 *
 * This software is copyrighted by and is the sole property of
 * VIA Networking Technologies, Inc. This software may only be used
 * in accordance with the corresponding license agreement. Any unauthorized
 * use, duplication, transmission, distribution, or disclosure of this
 * software is expressly forbidden.
 *
 * This software is provided by VIA Networking Technologies, Inc. "as is"
 * and any express or implied warranties, including, but not limited to, the
 * implied warranties of merchantability and fitness for a particular purpose
 * are disclaimed. In no event shall VIA Networking Technologies, Inc.
 * be liable for any direct, indirect, incidental, special, exemplary, or
 * consequential damages.
 *
 * File: rc4.c
 *
 * 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));
}