/*

   * Copyright (c) 1996, 2003 VIA Networking Technologies, Inc.
   * All rights reserved.

   *
   * 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.
   *

   * File: rc4.c
   *

   * Purpose:
   *
   * Functions:
   *
   * Revision History:
   *
   * Author: Kyle Hsu
   *
   * Date: Sep 4, 2002
   *
   */

  #include "rc4.h"

  void rc4_init(PRC4Ext pRC4, unsigned char *pbyKey, unsigned int cbKey_len)

  {

  	unsigned int ust1, ust2;
  	unsigned int keyindex;
  	unsigned int stateindex;
  	unsigned char *pbyst;
  	unsigned int idx;

  	pbyst = pRC4->abystate;
  	pRC4->ux = 0;
  	pRC4->uy = 0;
  	for (idx = 0; idx < 256; idx++)
  		pbyst[idx] = (unsigned char)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] = (unsigned char)ust1;
  		pbyst[idx] = (unsigned char)ust2;
  		if (++keyindex >= cbKey_len)
  			keyindex = 0;
  	}

  }

  unsigned int rc4_byte(PRC4Ext pRC4)

  {

  	unsigned int ux;
  	unsigned int uy;
  	unsigned int ustx, usty;
  	unsigned char *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] = (unsigned char)ustx;
  	pbyst[ux] = (unsigned char)usty;

  	return pbyst[(ustx + usty) & 0xff];

  }

  void rc4_encrypt(PRC4Ext pRC4, unsigned char *pbyDest,

  		 unsigned char *pbySrc, unsigned int cbData_len)

  {

  	unsigned int ii;

  	for (ii = 0; ii < cbData_len; ii++)
  		pbyDest[ii] = (unsigned char)(pbySrc[ii] ^ rc4_byte(pRC4));

  }