001 /* DESKeySpec -- Keys for 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 keys, which are arrays
046 * of 8 bytes.
047 *
048 * @author Casey Marshall (csm@gnu.org)
049 * @since 1.4
050 */
051 public class DESKeySpec implements KeySpec
052 {
053
054 // Constants.
055 // ------------------------------------------------------------------------
056
057 /**
058 * The length of a DES key, in bytes.
059 */
060 public static final int DES_KEY_LEN = 8;
061
062 /**
063 * The key bytes.
064 */
065 private byte[] key;
066
067 // Constructors.
068 // ------------------------------------------------------------------------
069
070 /**
071 * Create a new DES key spec, copying the first 8 bytes from the
072 * byte array.
073 *
074 * @param key The key bytes.
075 * @throws java.security.InvalidKeyException If there are less than 8
076 * bytes in the array.
077 */
078 public DESKeySpec(byte[] key) throws InvalidKeyException
079 {
080 this(key, 0);
081 }
082
083 /**
084 * Create a new DES key spec, starting at <code>offset</code> in
085 * the byte array. The first 8 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 8
091 * bytes starting at <code>offset</code>.
092 */
093 public DESKeySpec(byte[] key, int offset) throws InvalidKeyException
094 {
095 if (key.length - offset < DES_KEY_LEN)
096 {
097 throw new InvalidKeyException("DES keys must be 8 bytes long");
098 }
099 this.key = new byte[DES_KEY_LEN];
100 System.arraycopy(key, offset, this.key, 0, DES_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+7]</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_KEY_LEN)
121 {
122 throw new InvalidKeyException("DES keys must be 8 bytes long");
123 }
124 boolean parity = false;
125 boolean oddbits = false;
126 for (int i = 0; i < DES_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 /**
139 * One-half of the weak and semiweak DES keys (the other half are the
140 * complements of these).
141 */
142 private static final byte[][] WEAK_KEYS = new byte[][] {
143 { 0, 0, 0, 0, 0, 0, 0, 0 }, // 0000 0000 0000 0000
144 { -1, -1, -1, -1, 0, 0, 0, 0 }, // ffff ffff 0000 0000
145 { 1, 1, 1, 1, 1, 1, 1, 1 }, // 0101 0101 0101 0101
146 { 31, 31, 31, 31, 14, 14, 14, 14 }, // 1f1f 1f1f 0e0e 0e0e
147 { 1, -2, 1, -2, 1, -2, 1, -2 }, // 01fe 01fe 01fe 01fe
148 { 31, -32, 31, -32, -32, 31, -32, 31 }, // 1fe0 1fe0 0e1f 0e1f
149 { 1, -32, 1, -32, 1, -15, 1, -15 }, // 01e0 01e0 01f1 01f1
150 { 31, -2, 31, -2, 14, -2, 14, -2 }, // 1ffe 1ffe 0efe 0efe
151 { 1, 31, 1, 31, 1, 14, 1, 14 }, // 011f 011f 010e 010e
152 { -32, -2, -32, -2, -15, -2, -15, -2 }, // e0fe e0fe f1fe f1fe
153 };
154
155 /**
156 * Tests if the bytes between <code>[offset, offset+7]</code>
157 * constitute a weak or semi-weak DES key.
158 *
159 * @param key The key bytes to check.
160 * @param offset The offset in the byte array to start.
161 * @return true If the key bytes are a weak key.
162 */
163 public static boolean isWeak(byte[] key, int offset)
164 throws InvalidKeyException
165 {
166 if (key.length - offset < DES_KEY_LEN)
167 {
168 throw new InvalidKeyException("DES keys must be 8 bytes long");
169 }
170 for (int i = 0; i < WEAK_KEYS.length; i++)
171 {
172 if (equalsOrComplementEquals(key, offset, WEAK_KEYS[i]))
173 {
174 return true;
175 }
176 }
177 return false;
178 }
179
180 /**
181 * This method returns true if the first 8 bytes starting at
182 * <code>off</code> in <code>a</code> equal the first 8 bytes in
183 * <code>b</code>, or equal the <i>complement</i> of the first 8 bytes
184 * in <code>b</code>.
185 *
186 * @param a The first byte array.
187 * @param off The index into the first byte array.
188 * @param b The second byte array.
189 * @return <code>a == b || a == ~b</code>
190 */
191 private static boolean equalsOrComplementEquals(byte[] a, int off, byte[] b)
192 {
193 boolean result = true;
194 for (int i = 0; i < DES_KEY_LEN; i++)
195 {
196 result &= a[off+i] == b[i];
197 }
198 if (result) return true;
199 result = true;
200 for (int i = 0; i < DES_KEY_LEN; i++)
201 {
202 result &= a[off+i] == (~b[i]);
203 }
204 return result;
205 }
206
207 // Instance methods.
208 // ------------------------------------------------------------------------
209
210 /**
211 * Return the key as a byte array. This method does not copy the byte
212 * array.
213 *
214 * @return The key bytes.
215 */
216 public byte[] getKey()
217 {
218 return key;
219 }
220 }