/* UMacGenerator.java --
Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.
This file is a part of GNU Classpath.
GNU Classpath 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 of the License, or (at
your option) any later version.
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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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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.prng;
import gnu.java.security.Registry;
import gnu.java.security.prng.BasePRNG;
import gnu.java.security.prng.LimitReachedException;
import gnu.javax.crypto.cipher.CipherFactory;
import gnu.javax.crypto.cipher.IBlockCipher;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.security.InvalidKeyException;
/**
* <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>
* <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 Integer} with a value between <code>0</code> and
* <code>255</code>). Using the same key, but different indices, generates
* different pseudorandom outputs.
* <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 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 Integer}) is missing or undefined in the initialisation
* <code>Map</code>, then the cipher's <em>default</em> block size is used.
* <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>
* References:
* <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>
*/
public class UMacGenerator
extends BasePRNG
implements Cloneable
{
/**
* 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>.
*/
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;
/** Trivial 0-arguments constructor. */
public UMacGenerator()
{
super(Registry.UMAC_PRNG);
}
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, Integer.valueOf(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);
}
}