Source for gnu.javax.crypto.pad.IPad

   1: /* IPad.java --
   2:    Copyright (C) 2001, 2002, 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.pad;
  40: 
  41: import java.util.Map;
  42: 
  43: /**
  44:  * The basic visible methods, and attribute names, of every padding algorithm.
  45:  * <p>
  46:  * Padding algorithms serve to <i>pad</i> and <i>unpad</i> byte arrays usually
  47:  * as the last step in an <i>encryption</i> or respectively a <i>decryption</i>
  48:  * operation. Their input buffers are usually those processed by instances of
  49:  * {@link gnu.javax.crypto.mode.IMode} and/or
  50:  * {@link gnu.javax.crypto.cipher.IBlockCipher}.
  51:  */
  52: public interface IPad
  53: {
  54:   /**
  55:    * Property name of the block size in which to operate the padding algorithm.
  56:    * The value associated with this property name is taken to be a positive
  57:    * {@link Integer} greater than zero.
  58:    */
  59:   String PADDING_BLOCK_SIZE = "gnu.crypto.pad.block.size";
  60: 
  61:   /** @return the canonical name of this instance. */
  62:   String name();
  63: 
  64:   /**
  65:    * Initialises the padding scheme with a designated block size.
  66:    *
  67:    * @param bs the designated block size.
  68:    * @exception IllegalStateException if the instance is already initialised.
  69:    * @exception IllegalArgumentException if the block size value is invalid.
  70:    */
  71:   void init(int bs) throws IllegalStateException;
  72: 
  73:   /**
  74:    * Initialises the algorithm with designated attributes. Names, valid and/or
  75:    * recognisable by all concrete implementations are described in the class
  76:    * documentation above. Other algorithm-specific attributes MUST be documented
  77:    * in the implementation class of that padding algorithm.
  78:    *
  79:    * @param attributes a set of name-value pairs that describes the desired
  80:    *          future behaviour of this instance.
  81:    * @exception IllegalStateException if the instance is already initialised.
  82:    * @exception IllegalArgumentException if the block size value is invalid.
  83:    */
  84:   void init(Map attributes) throws IllegalStateException;
  85: 
  86:   /**
  87:    * Returns the byte sequence that should be appended to the designated input.
  88:    *
  89:    * @param in the input buffer containing the bytes to pad.
  90:    * @param offset the starting index of meaningful data in <i>in</i>.
  91:    * @param length the number of meaningful bytes in <i>in</i>.
  92:    * @return the possibly 0-byte long sequence to be appended to the designated
  93:    *         input.
  94:    */
  95:   byte[] pad(byte[] in, int offset, int length);
  96: 
  97:   /**
  98:    * Returns the number of bytes to discard from a designated input buffer.
  99:    *
 100:    * @param in the input buffer containing the bytes to unpad.
 101:    * @param offset the starting index of meaningful data in <i>in</i>.
 102:    * @param length the number of meaningful bytes in <i>in</i>.
 103:    * @return the number of bytes to discard, to the left of index position
 104:    *         <code>offset + length</code> in <i>in</i>. In other words, if
 105:    *         the return value of a successful invocation of this method is
 106:    *         <code>result</code>, then the unpadded byte sequence will be
 107:    *         <code>offset + length - result</code> bytes in <i>in</i>,
 108:    *         starting from index position <code>offset</code>.
 109:    * @exception WrongPaddingException if the data is not terminated with the
 110:    *              expected padding bytes.
 111:    */
 112:   int unpad(byte[] in, int offset, int length) throws WrongPaddingException;
 113: 
 114:   /**
 115:    * Resets the scheme instance for re-initialisation and use with other
 116:    * characteristics. This method always succeeds.
 117:    */
 118:   void reset();
 119: 
 120:   /**
 121:    * A basic symmetric pad/unpad test.
 122:    *
 123:    * @return <code>true</code> if the implementation passes a basic symmetric
 124:    *         self-test. Returns <code>false</code> otherwise.
 125:    */
 126:   boolean selfTest();
 127: }