Source for javax.crypto.spec.DESedeKeySpec

   1: /* DESedeKeySpec.java -- Keys for triple-DES.
   2:    Copyright (C) 2004  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package javax.crypto.spec;
  40: 
  41: import java.security.InvalidKeyException;
  42: import java.security.spec.KeySpec;
  43: 
  44: /**
  45:  * This class is a transparent wrapper for DES-EDE (Triple-DES) keys,
  46:  * which are arrays of 24 bytes.
  47:  *
  48:  * @author Casey Marshall (csm@gnu.org)
  49:  * @since 1.4
  50:  */
  51: public class DESedeKeySpec implements KeySpec
  52: {
  53: 
  54:   // Constants.
  55:   // ------------------------------------------------------------------------
  56: 
  57:   /**
  58:    * The length of a triple-DES key, in bytes.
  59:    */
  60:   public static final int DES_EDE_KEY_LEN = 24;
  61: 
  62:   /**
  63:    * The key bytes.
  64:    */
  65:   private byte[] key;
  66: 
  67:   // Constructors.
  68:   // ------------------------------------------------------------------------
  69: 
  70:   /**
  71:    * Create a new DES-EDE key spec, copying the first 24 bytes from the
  72:    * byte array.
  73:    *
  74:    * @param key The key bytes.
  75:    * @throws java.security.InvalidKeyException If there are less than 24
  76:    *         bytes in the array.
  77:    */
  78:   public DESedeKeySpec(byte[] key) throws InvalidKeyException
  79:   {
  80:     this(key, 0);
  81:   }
  82: 
  83:   /**
  84:    * Create a new DES-EDE key spec, starting at <code>offset</code> in
  85:    * the byte array. The first 24 bytes starting at <code>offset</code>
  86:    * are copied.
  87:    *
  88:    * @param key    The key bytes.
  89:    * @param offset The offset into the byte array at which to begin.
  90:    * @throws java.security.InvalidKeyException If there are less than 24
  91:    *         bytes starting at <code>offset</code>.
  92:    */
  93:   public DESedeKeySpec(byte[] key, int offset) throws InvalidKeyException
  94:   {
  95:     if (key.length - offset < DES_EDE_KEY_LEN)
  96:       {
  97:         throw new InvalidKeyException("DES-EDE keys must be 24 bytes long");
  98:       }
  99:     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: }