text: /*
   *  An implementation of the ARCFOUR algorithm
   *
   *  Based on XySSL: Copyright (C) 2006-2008  Christophe Devine
   *
   *  Copyright (C) 2009  Paul Bakker <polarssl_maintainer at polarssl dot org>
   *
   *  All rights reserved.
   *
   *  Redistribution and use in source and binary forms, with or without
   *  modification, are permitted provided that the following conditions
   *  are met:
   *  
   *    * Redistributions of source code must retain the above copyright
   *      notice, this list of conditions and the following disclaimer.
   *    * Redistributions in binary form must reproduce the above copyright
   *      notice, this list of conditions and the following disclaimer in the
   *      documentation and/or other materials provided with the distribution.
   *    * Neither the names of PolarSSL or XySSL nor the names of its contributors
   *      may be used to endorse or promote products derived from this software
   *      without specific prior written permission.
   *  
   *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   *  "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 THE COPYRIGHT
   *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
   *  TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  /*
   *  The ARCFOUR algorithm was publicly disclosed on 94/09.
   *
   *  http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0
   */
  
  #include "ppp_opts.h"
  #if PPP_SUPPORT && PPP_INCLUDED_POLARSSL_ARC4
  
  #include "polarssl/arc4.h"
  /*
   * ARC4 key schedule
   */
  void arc4_setup( arc4_context *ctx, unsigned char *key, int keylen )
  {
      int i, j, k, a;
      unsigned char *m;
  
      ctx->x = 0;
      ctx->y = 0;
      m = ctx->m;
  
      for( i = 0; i < 256; i++ )
          m[i] = (unsigned char) i;
  
      j = k = 0;
  
      for( i = 0; i < 256; i++, k++ )
      {
          if( k >= keylen ) k = 0;
  
          a = m[i];
          j = ( j + a + key[k] ) & 0xFF;
          m[i] = m[j];
          m[j] = (unsigned char) a;
      }
  }
  
  /*
   * ARC4 cipher function
   */
  void arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen )
  {
      int i, x, y, a, b;
      unsigned char *m;
  
      x = ctx->x;
      y = ctx->y;
      m = ctx->m;
  
      for( i = 0; i < buflen; i++ )
      {
          x = ( x + 1 ) & 0xFF; a = m[x];
          y = ( y + a ) & 0xFF; b = m[y];
  
          m[x] = (unsigned char) b;
          m[y] = (unsigned char) a;
  
          buf[i] = (unsigned char)
              ( buf[i] ^ m[(unsigned char)( a + b )] );
      }
  
      ctx->x = x;
      ctx->y = y;
  }
  
  #endif /* PPP_SUPPORT && PPP_INCLUDED_POLARSSL_DES */
  