rc4engine.java

eclipseme的最新版本的source,欢迎j2me程序员使用

/*
 * Original source code was from Bouncy Castle
 * Copyright (c) 2000 The Legion Of The Bouncy Castle (http://www.bouncycastle.org) 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this 
 * software and associated documentation files (the "Software"), to deal in the Software 
 * without restriction, including without limitation the rights to use, copy, modify, merge, 
 * publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons 
 * to whom the Software is furnished to do so, subject to the following conditions: 
 * The above copyright notice and this permission notice shall be included in all copies 
 * or substantial portions of the Software. 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR 
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE 
 * FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
 * SOFTWARE
 */

package eclipseme.core.signing;

/**
 * RC4 engine implementation.<br/>
 * Original source code was from Bouncy Castle.<br/>
 * Copyright (c) 2000 The Legion Of The Bouncy Castle (http://www.bouncycastle.org) 
 */
public class RC4Engine
{
    private final static int STATE_LENGTH = 256;

    /*
     * variables to hold the state of the RC4 engine
     * during encryption and decryption
     */

    private byte[]      engineState = null;
    private int         x = 0;
    private int         y = 0;
    private byte[]      workingKey = null;

    public byte returnByte(byte in)
    {
        x = (x + 1) & 0xff;
        y = (engineState[x] + y) & 0xff;

        // swap
        byte tmp = engineState[x];
        engineState[x] = engineState[y];
        engineState[y] = tmp;

        // xor
        return (byte)(in ^ engineState[(engineState[x] + engineState[y]) & 0xff]);
    }

    public void processBytes(
        byte[]     in, 
        int     inOff, 
        int     len, 
        byte[]     out, 
        int     outOff
    )
    {
        if ((inOff + len) > in.length)
        {
            throw new IllegalArgumentException("input buffer too short");
        }

        if ((outOff + len) > out.length)
        {
            throw new IllegalArgumentException("output buffer too short");
        }

        for (int i = 0; i < len ; i++)
        {
            x = (x + 1) & 0xff;
            y = (engineState[x] + y) & 0xff;

            // swap
            byte tmp = engineState[x];
            engineState[x] = engineState[y];
            engineState[y] = tmp;

            // xor
            out[i+outOff] = (byte)(in[i + inOff]
                    ^ engineState[(engineState[x] + engineState[y]) & 0xff]);
        }
    }

    public void reset()
    {
        setKey(workingKey);
    }

    // Private implementation

    public void setKey(byte[] keyBytes)
    {
        workingKey = keyBytes;

        // System.out.println("the key length is ; "+ workingKey.length);

        x = 0;
        y = 0;

        if (engineState == null)
        {
            engineState = new byte[STATE_LENGTH];
        }

        // reset the state of the engine
        for (int i=0; i < STATE_LENGTH; i++)
        {
            engineState[i] = (byte)i;
        }
        
        int i1 = 0;
        int i2 = 0;

        for (int i=0; i < STATE_LENGTH; i++)
        {
            i2 = ((keyBytes[i1] & 0xff) + engineState[i] + i2) & 0xff;
            // do the byte-swap inline
            byte tmp = engineState[i];
            engineState[i] = engineState[i2];
            engineState[i2] = tmp;
            i1 = (i1+1) % keyBytes.length; 
        }
    }
}