Source for gnu.javax.crypto.mode.ModeFactory

   1: /* ModeFactory.java --
   2:    Copyright (C) 2001, 2002, 2004, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is a 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 of the License, or (at
   9: your option) 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; if not, write to the Free Software
  18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19: 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 gnu.javax.crypto.mode;
  40: 
  41: import gnu.java.security.Registry;
  42: 
  43: import gnu.javax.crypto.cipher.CipherFactory;
  44: import gnu.javax.crypto.cipher.IBlockCipher;
  45: 
  46: import java.util.Collections;
  47: import java.util.HashSet;
  48: import java.util.Iterator;
  49: import java.util.Set;
  50: 
  51: /**
  52:  * A <i>Factory</i> to instantiate block cipher modes of operations.
  53:  */
  54: public class ModeFactory
  55:     implements Registry
  56: {
  57:   private static Set names;
  58: 
  59:   /** Trivial constructor to enforce Singleton pattern. */
  60:   private ModeFactory()
  61:   {
  62:     super();
  63:   }
  64: 
  65:   /**
  66:    * Returns an instance of a block cipher mode of operations given its name and
  67:    * characteristics of the underlying block cipher.
  68:    *
  69:    * @param mode the case-insensitive name of the mode of operations.
  70:    * @param cipher the case-insensitive name of the block cipher.
  71:    * @param cipherBlockSize the block size, in bytes, of the underlying cipher.
  72:    * @return an instance of the block cipher algorithm, operating in a given
  73:    *         mode of operations, or <code>null</code> if none found.
  74:    * @exception InternalError if either the mode or the underlying block cipher
  75:    *              implementation does not pass its self-test.
  76:    */
  77:   public static IMode getInstance(String mode, String cipher,
  78:                                   int cipherBlockSize)
  79:   {
  80:     if (mode == null || cipher == null)
  81:       return null;
  82: 
  83:     mode = mode.trim();
  84:     cipher = cipher.trim();
  85:     IBlockCipher cipherImpl = CipherFactory.getInstance(cipher);
  86:     if (cipherImpl == null)
  87:       return null;
  88: 
  89:     return getInstance(mode, cipherImpl, cipherBlockSize);
  90:   }
  91: 
  92:   public static IMode getInstance(String mode, IBlockCipher cipher,
  93:                                   int cipherBlockSize)
  94:   {
  95:     // ensure that cipherBlockSize is valid for the chosen underlying cipher
  96:     boolean ok = false;
  97:     for (Iterator it = cipher.blockSizes(); it.hasNext();)
  98:       {
  99:         ok = (cipherBlockSize == ((Integer) it.next()).intValue());
 100:         if (ok)
 101:           break;
 102:       }
 103:     if (! ok)
 104:       throw new IllegalArgumentException("cipherBlockSize");
 105:     IMode result = null;
 106:     if (mode.equalsIgnoreCase(ECB_MODE))
 107:       result = new ECB(cipher, cipherBlockSize);
 108:     else if (mode.equalsIgnoreCase(CTR_MODE))
 109:       result = new CTR(cipher, cipherBlockSize);
 110:     else if (mode.equalsIgnoreCase(ICM_MODE))
 111:       result = new ICM(cipher, cipherBlockSize);
 112:     else if (mode.equalsIgnoreCase(OFB_MODE))
 113:       result = new OFB(cipher, cipherBlockSize);
 114:     else if (mode.equalsIgnoreCase(CBC_MODE))
 115:       result = new CBC(cipher, cipherBlockSize);
 116:     else if (mode.equalsIgnoreCase(CFB_MODE))
 117:       result = new CFB(cipher, cipherBlockSize);
 118:     else if (mode.equalsIgnoreCase(EAX_MODE))
 119:       result = new EAX(cipher, cipherBlockSize);
 120: 
 121:     if (result != null && ! result.selfTest())
 122:       throw new InternalError(result.name());
 123: 
 124:     return result;
 125:   }
 126: 
 127:   /**
 128:    * Returns a {@link Set} of names of mode supported by this <i>Factory</i>.
 129:    *
 130:    * @return a {@link Set} of mode names (Strings).
 131:    */
 132:   public static final Set getNames()
 133:   {
 134:     synchronized (ModeFactory.class)
 135:       {
 136:         if (names == null)
 137:           {
 138:             HashSet hs = new HashSet();
 139:             hs.add(ECB_MODE);
 140:             hs.add(CTR_MODE);
 141:             hs.add(ICM_MODE);
 142:             hs.add(OFB_MODE);
 143:             hs.add(CBC_MODE);
 144:             hs.add(CFB_MODE);
 145:             hs.add(EAX_MODE);
 146:             names = Collections.unmodifiableSet(hs);
 147:           }
 148:       }
 149:     return names;
 150:   }
 151: }