001/* DESKeySpec -- Keys for DES. 002 Copyright (C) 2004 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package javax.crypto.spec; 040 041import java.security.InvalidKeyException; 042import 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 */ 051public 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}