/* * Copyright (C) 1995, 1996 Systemics Ltd (http://www.systemics.com/) * All rights reserved. * * This library and applications are FREE FOR COMMERCIAL AND NON-COMMERCIAL USE * as long as the conditions within the COPYRIGHT file are adhered to. * */package java.crypt;/** * This class implements the DES block cipher. * * <p>The native code DES implementation used by the class was * developed by, and is owned by, Eric Young (eay@mincom.oz.au) * <p>Copyright (C) 1995, 1996 Systemics Ltd (http://www.systemics.com/) * All rights reserved. * * @version 1.00, 14/12/1995 * @author      Systemics (Michael Wynn) */public final class DES extends BlockCipher{    /**     * This is the length of a block.     */    public static final int BLOCK_LENGTH = 8;    /**     * This is the length of a the user key.     */    public static final int KEY_LENGTH = 8;        /**     * this loads the dll with the native code.     */    static    {        System.loadLibrary( "des" );    }    /**     * This is the length of the internal buffer for the native code.     */    private static final int INTERNAL_KEY_LENGTH = 128;    /**     * This is the internal buffer with the expanded encrypt key.     */    private byte ks[] = null;     /**     * This creates a DES block cipher from a byte array of the correct length.     * @param userKey    the user key.     */    public DES( byte userKey[] )     {        ks = new byte[INTERNAL_KEY_LENGTH];        if ( userKey.length != KEY_LENGTH )            throw new CryptoError( "DES: User key length wrong" );        set_ks( userKey );    }    /**     * Encrypt a block.	 * The in and out buffers can be the same.     * @param in The data to be encrypted.     * @param in_offset   The start of data within the in buffer.     * @param out The encrypted data.     * @param out_offset  The start of data within the out buffer.     */    protected void     blockEncrypt( byte in[], int in_offset, byte out[], int out_offset )    {        if ( ks == null )            throw new CryptoError( "DES: User key not set" );        do_des( in, in_offset, out, out_offset, true );    }    /**     * Decrypt a block.	 * The in and out buffers can be the same.     * @param in The data to be decrypted.     * @param in_offset   The start of data within the in buffer.     * @param out The decrypted data.     * @param out_offset  The start of data within the out buffer.     */    protected void    blockDecrypt( byte in[], int in_offset, byte out[], int out_offset )    {        if ( ks == null )            throw new CryptoError( "DES: User key not set." );        do_des( in, in_offset, out, out_offset, false );    }    /**     * Return the block length of this cipher.     * @returns the block length of this cipher.     */    public int     blockLength()    {        return BLOCK_LENGTH;    }    /**     * Return the key length for this cipher.     * @returns the key length of this cipher.     */    public int     keyLength()    {        return KEY_LENGTH;    }    // these are the native functions that implement the DES algorithm.    /**     * This function expands the user key to an internal form.     */    private native void set_ks( byte userKey[] );    /**     * Encrypt/decrypt the block (depending upon encrypt flag)     */    private native void do_des( byte in[], int in_offset, byte out[], int out_offset, boolean encrypt );}