001    /* DESedeKeySpec.java -- Keys for triple-DES.
002       Copyright (C) 2004  Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package javax.crypto.spec;
040    
041    import java.security.InvalidKeyException;
042    import java.security.spec.KeySpec;
043    
044    /**
045     * This class is a transparent wrapper for DES-EDE (Triple-DES) keys,
046     * which are arrays of 24 bytes.
047     *
048     * @author Casey Marshall (csm@gnu.org)
049     * @since 1.4
050     */
051    public class DESedeKeySpec implements KeySpec
052    {
053    
054      // Constants.
055      // ------------------------------------------------------------------------
056    
057      /**
058       * The length of a triple-DES key, in bytes.
059       */
060      public static final int DES_EDE_KEY_LEN = 24;
061    
062      /**
063       * The key bytes.
064       */
065      private byte[] key;
066    
067      // Constructors.
068      // ------------------------------------------------------------------------
069    
070      /**
071       * Create a new DES-EDE key spec, copying the first 24 bytes from the
072       * byte array.
073       *
074       * @param key The key bytes.
075       * @throws java.security.InvalidKeyException If there are less than 24
076       *         bytes in the array.
077       */
078      public DESedeKeySpec(byte[] key) throws InvalidKeyException
079      {
080        this(key, 0);
081      }
082    
083      /**
084       * Create a new DES-EDE key spec, starting at <code>offset</code> in
085       * the byte array. The first 24 bytes starting at <code>offset</code>
086       * are copied.
087       *
088       * @param key    The key bytes.
089       * @param offset The offset into the byte array at which to begin.
090       * @throws java.security.InvalidKeyException If there are less than 24
091       *         bytes starting at <code>offset</code>.
092       */
093      public DESedeKeySpec(byte[] key, int offset) throws InvalidKeyException
094      {
095        if (key.length - offset < DES_EDE_KEY_LEN)
096          {
097            throw new InvalidKeyException("DES-EDE keys must be 24 bytes long");
098          }
099        this.key = new byte[DES_EDE_KEY_LEN];
100        System.arraycopy(key, offset, this.key, 0, DES_EDE_KEY_LEN);
101      }
102    
103      // Class methods.
104      // ------------------------------------------------------------------------
105    
106      /**
107       * Returns whether or not the given key is <i>parity adjusted</i>;
108       * i.e. every byte in the key has an odd number of "1" bits.
109       *
110       * @param key    The key bytes, considered between <code>[offset,
111       *               offset+23]</code>
112       * @param offset The offset into the byte array at which to begin.
113       * @return True if all bytes have an odd number of "1" bits.
114       * @throws java.security.InvalidKeyException If there are not enough
115       *         bytes in the array.
116       */
117      public static boolean isParityAdjusted(byte[] key, int offset)
118        throws InvalidKeyException
119      {
120        if (key.length - offset < DES_EDE_KEY_LEN)
121          {
122            throw new InvalidKeyException("DES-EDE keys must be 24 bytes long");
123          }
124        boolean parity = false;
125        boolean oddbits = false;
126        for (int i = 0; i < DES_EDE_KEY_LEN; i++)
127          {
128            oddbits = false;
129            for (int j = 0; j < 8; j++)
130              {
131                oddbits ^= (key[i+offset] & 1 << j) != 0;
132              }
133            parity &= oddbits;
134          }
135        return parity;
136      }
137    
138      // Instance methods.
139      // ------------------------------------------------------------------------
140    
141      /**
142       * Return the key as a byte array. This method does not copy the byte
143       * array.
144       *
145       * @return The key bytes.
146       */
147      public byte[] getKey()
148      {
149        return key;
150      }
151    }