source: other-projects/trunk/gs3-release-maker/tasks/sshtaskdef/src/mindbright/security/RC4.java@ 14627

/******************************************************************************
 *
 * Copyright (c) 1998,99 by Mindbright Technology AB, Stockholm, Sweden.
 *                 www.mindbright.se, [email protected]
 *
 * 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.
 *
 *****************************************************************************
 * $Author: mats $
 * $Date: 1999/07/19 17:13:49 $
 * $Name: rel1-2-1 $
 *****************************************************************************/
/*
 * !!! Author's comment: I don't know if there are any copyright
 * issues here but this code is so trivial so I guess there are not
 * (apart from the name RC4 which I believe is a trademark...).
 */
package mindbright.security;

public final class RC4 extends Cipher {
  int    x;
  int    y;
  byte[] state = new byte[256];

  final int arcfour_byte() {
    int x;
    int y;
    int sx, sy;

    x = (this.x + 1) & 0xff;
    sx = (int)state[x];
    y = (sx + this.y) & 0xff;
    sy = (int)state[y];
    this.x = x;
    this.y = y;
    state[y] = (byte)(sx & 0xff);
    state[x] = (byte)(sy & 0xff);
    return (int)state[((sx + sy) & 0xff)];
  }

  public synchronized void encrypt(byte[] src, int srcOff, byte[] dest, int destOff, int len) {
    int end = srcOff + len;
    for(int si = srcOff, di = destOff; si < end; si++, di++)
      dest[di] = (byte)(((int)src[si] ^ arcfour_byte()) & 0xff);
  }

  public void decrypt(byte[] src, int srcOff, byte[] dest, int destOff, int len) {
    encrypt(src, srcOff, dest, destOff, len);
  }

  public void setKey(byte[] key) {
    int t, u;
    int keyindex;
    int stateindex;
    int counter;
    
    for(counter = 0; counter < 256; counter++)
      state[counter] = (byte)counter;
    keyindex = 0;
    stateindex = 0;
    for(counter = 0; counter < 256; counter++) {
      t = (int)state[counter];
      stateindex = (stateindex + key[keyindex] + t) & 0xff;
      u = (int)state[stateindex];
      state[stateindex] = (byte)(t & 0xff);
      state[counter] = (byte)(u & 0xff);
      if(++keyindex >= key.length)
    keyindex = 0;
    }
  }

}