package gnu.crypto.prng;
// ----------------------------------------------------------------------------
// $Id: UMacGenerator.java,v 1.7 2005/10/06 04:24:17 rsdio Exp $
//
// Copyright (C) 2001, 2002, Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
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// along with this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
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// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
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// you permission to link this library with independent modules to
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// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
import gnu.crypto.Registry;
import gnu.crypto.cipher.CipherFactory;
import gnu.crypto.cipher.IBlockCipher;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.security.InvalidKeyException;
/**
* <p><i>KDF</i>s (Key Derivation Functions) are used to stretch user-supplied
* key material to specific size(s) required by high level cryptographic
* primitives. Described in the <A
* HREF="http://www.ietf.org/internet-drafts/draft-krovetz-umac-01.txt">UMAC</A>
* paper, this function basically operates an underlying <em>symmetric key block
* cipher</em> instance in output feedback mode (OFB), as a <b>strong</b>
* pseudo-random number generator.</p>
*
* <p><code>UMacGenerator</code> requires an <em>index</em> parameter
* (initialisation parameter <code>gnu.crypto.prng.umac.kdf.index</code> taken
* to be an instance of {@link java.lang.Integer} with a value between
* <code>0</code> and <code>255</code>). Using the same key, but different
* indices, generates different pseudorandom outputs.</p>
*
* <p>This implementation generalises the definition of the
* <code>UmacGenerator</code> algorithm to allow for other than the AES symetric
* key block cipher algorithm (initialisation parameter
* <code>gnu.crypto.prng.umac.cipher.name</code> taken to be an instance of
* {@link java.lang.String}). If such a parameter is not defined/included in the
* initialisation <code>Map</code>, then the "Rijndael" algorithm is used.
* Furthermore, if the initialisation parameter
* <code>gnu.crypto.cipher.block.size</code> (taken to be a instance of {@link
* java.lang.Integer}) is missing or undefined in the initialisation <code>Map
* </code>, then the cipher's <em>default</em> block size is used.</p>
*
* <p><b>NOTE</b>: Rijndael is used as the default symmetric key block cipher
* algorithm because, with its default block and key sizes, it is the AES. Yet
* being Rijndael, the algorithm offers more versatile block and key sizes which
* may prove to be useful for generating "longer" key streams.</p>
*
* <p>References:</p>
*
* <ol>
* <li><a href="http://www.ietf.org/internet-drafts/draft-krovetz-umac-01.txt">
* UMAC</a>: Message Authentication Code using Universal Hashing.<br>
* T. Krovetz, J. Black, S. Halevi, A. Hevia, H. Krawczyk, and P. Rogaway.</li>
* </ol>
*
* @version $Revision: 1.7 $
*/
public class UMacGenerator extends BasePRNG implements Cloneable {
// Constants and variables
// -------------------------------------------------------------------------
/**
* <p>Property name of the KDF <code>index</code> value to use in this
* instance. The value is taken to be an {@link Integer} less than
* <code>256</code>.</p>
*/
public static final String INDEX = "gnu.crypto.prng.umac.index";
/** The name of the underlying symmetric key block cipher algorithm. */
public static final String CIPHER = "gnu.crypto.prng.umac.cipher.name";
/** The generator's underlying block cipher. */
private IBlockCipher cipher;
// Constructor(s)
// -------------------------------------------------------------------------
/** Trivial 0-arguments constructor. */
public UMacGenerator() {
super(Registry.UMAC_PRNG);
}
// Class methods
// -------------------------------------------------------------------------
// Instance methods
// -------------------------------------------------------------------------
// Implementation of abstract methods in BasePRNG --------------------------
public void setup(Map attributes) {
boolean newCipher = true;
String cipherName = (String) attributes.get(CIPHER);
if (cipherName == null) {
if (cipher == null) { // happy birthday
cipher = CipherFactory.getInstance(Registry.RIJNDAEL_CIPHER);
} else { // we already have one. use it as is
newCipher = false;
}
} else {
cipher = CipherFactory.getInstance(cipherName);
}
// find out what block size we should use it in
int cipherBlockSize = 0;
Integer bs = (Integer) attributes.get(IBlockCipher.CIPHER_BLOCK_SIZE);
if (bs != null) {
cipherBlockSize = bs.intValue();
} else {
if (newCipher) { // assume we'll use its default block size
cipherBlockSize = cipher.defaultBlockSize();
} // else use as is
}
// get the key material
byte[] key = (byte[]) attributes.get(IBlockCipher.KEY_MATERIAL);
if (key == null) {
throw new IllegalArgumentException(IBlockCipher.KEY_MATERIAL);
}
int keyLength = key.length;
// ensure that keyLength is valid for the chosen underlying cipher
boolean ok = false;
for (Iterator it = cipher.keySizes(); it.hasNext(); ) {
ok = (keyLength == ((Integer) it.next()).intValue());
if (ok) {
break;
}
}
if (!ok) {
throw new IllegalArgumentException("key length");
}
// ensure that remaining params make sense
int index = -1;
Integer i = (Integer) attributes.get(INDEX);
if (i != null) {
index = i.intValue();
if (index < 0 || index > 255) {
throw new IllegalArgumentException(INDEX);
}
}
// now initialise the underlying cipher
Map map = new HashMap();
if (cipherBlockSize != 0) { // only needed if new or changed
map.put(IBlockCipher.CIPHER_BLOCK_SIZE, new Integer(cipherBlockSize));
}
map.put(IBlockCipher.KEY_MATERIAL, key);
try {
cipher.init(map);
} catch (InvalidKeyException x) {
throw new IllegalArgumentException(IBlockCipher.KEY_MATERIAL);
}
buffer = new byte[cipher.currentBlockSize()];
buffer[cipher.currentBlockSize() - 1] = (byte) index;
try {
fillBlock();
} catch (LimitReachedException impossible) {
}
}
public void fillBlock() throws LimitReachedException {
cipher.encryptBlock(buffer, 0, buffer, 0);
}
}