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gnu.javax.crypto.prng

Class UMacGenerator

Implemented Interfaces:
Cloneable, IRandom
public class UMacGenerator
extends BasePRNG
implements Cloneable
KDFs (Key Derivation Functions) are used to stretch user-supplied key material to specific size(s) required by high level cryptographic primitives. Described in the UMAC paper, this function basically operates an underlying symmetric key block cipher instance in output feedback mode (OFB), as a strong pseudo-random number generator.

UMacGenerator requires an index parameter (initialisation parameter gnu.crypto.prng.umac.kdf.index taken to be an instance of Integer with a value between 0 and 255). Using the same key, but different indices, generates different pseudorandom outputs.

This implementation generalises the definition of the UmacGenerator algorithm to allow for other than the AES symetric key block cipher algorithm (initialisation parameter gnu.crypto.prng.umac.cipher.name taken to be an instance of String). If such a parameter is not defined/included in the initialisation Map, then the "Rijndael" algorithm is used. Furthermore, if the initialisation parameter gnu.crypto.cipher.block.size (taken to be a instance of Integer) is missing or undefined in the initialisation Map, then the cipher's default block size is used.

NOTE: 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.

References:

  1. UMAC: Message Authentication Code using Universal Hashing.
    T. Krovetz, J. Black, S. Halevi, A. Hevia, H. Krawczyk, and P. Rogaway.

Field Summary

static String
CIPHER
The name of the underlying symmetric key block cipher algorithm.
static String
INDEX
Property name of the KDF index value to use in this instance.

Fields inherited from class gnu.java.security.prng.BasePRNG

buffer, initialised, name, ndx

Constructor Summary

UMacGenerator()
Trivial 0-arguments constructor.

Method Summary

void
fillBlock()
void
setup(Map<K,V> attributes)

Methods inherited from class gnu.java.security.prng.BasePRNG

addRandomByte, addRandomBytes, addRandomBytes, clone, fillBlock, init, isInitialised, name, nextByte, nextBytes, nextBytes, setup

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

CIPHER

public static final String CIPHER
The name of the underlying symmetric key block cipher algorithm.
Field Value:
"gnu.crypto.prng.umac.cipher.name"

INDEX

public static final String INDEX
Property name of the KDF index value to use in this instance. The value is taken to be an Integer less than 256.
Field Value:
"gnu.crypto.prng.umac.index"

Constructor Details

UMacGenerator

public UMacGenerator()
Trivial 0-arguments constructor.

Method Details

fillBlock

public void fillBlock()
            throws LimitReachedException
Overrides:
fillBlock in interface BasePRNG

setup

public void setup(Map<K,V> attributes)
Overrides:
setup in interface BasePRNG
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. GNU Classpath 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. You should have received a copy of the GNU General Public License along with GNU Classpath; if not, write to the Free Software 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 conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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