Source for javax.crypto.spec.DESKeySpec

   1: /* DESKeySpec -- Keys for 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 keys, which are arrays
  46:  * of 8 bytes.
  47:  *
  48:  * @author Casey Marshall (csm@gnu.org)
  49:  * @since 1.4
  50:  */
  51: public class DESKeySpec implements KeySpec
  52: {
  53: 
  54:   // Constants.
  55:   // ------------------------------------------------------------------------
  56: 
  57:   /**
  58:    * The length of a DES key, in bytes.
  59:    */
  60:   public static final int DES_KEY_LEN = 8;
  61: 
  62:   /**
  63:    * The key bytes.
  64:    */
  65:   private byte[] key;
  66: 
  67:   // Constructors.
  68:   // ------------------------------------------------------------------------
  69: 
  70:   /**
  71:    * Create a new DES key spec, copying the first 8 bytes from the
  72:    * byte array.
  73:    *
  74:    * @param key The key bytes.
  75:    * @throws java.security.InvalidKeyException If there are less than 8
  76:    *         bytes in the array.
  77:    */
  78:   public DESKeySpec(byte[] key) throws InvalidKeyException
  79:   {
  80:     this(key, 0);
  81:   }
  82: 
  83:   /**
  84:    * Create a new DES key spec, starting at <code>offset</code> in
  85:    * the byte array. The first 8 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 8
  91:    *         bytes starting at <code>offset</code>.
  92:    */
  93:   public DESKeySpec(byte[] key, int offset) throws InvalidKeyException
  94:   {
  95:     if (key.length - offset < DES_KEY_LEN)
  96:       {
  97:         throw new InvalidKeyException("DES keys must be 8 bytes long");
  98:       }
  99:     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: }