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 }