gnu.crypto.prng
Class UMacGenerator

java.lang.Object
  gnu.crypto.prng.BasePRNG
      gnu.crypto.prng.UMacGenerator

All Implemented Interfaces:

java.lang.Cloneable, IRandom

public class UMacGenerator

extends BasePRNG

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.

Version:

$Revision: 1.2 $

Field Summary

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

Fields inherited from class gnu.crypto.prng.BasePRNG

buffer, initialised, name, ndx

Constructor Summary

UMacGenerator()
Trivial 0-arguments constructor.

Method Summary

java.lang.Object	clone() Returns a clone copy of this instance.
void	fillBlock()
void	setup(java.util.Map attributes)

Methods inherited from class gnu.crypto.prng.BasePRNG

init, isInitialised, name, nextByte, nextBytes

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INDEX

public static final java.lang.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.

See Also:

Constant Field Values

CIPHER

public static final java.lang.String CIPHER

The name of the underlying symmetric key block cipher algorithm.

See Also:

Constant Field Values

Constructor Detail

UMacGenerator

public UMacGenerator()

Trivial 0-arguments constructor.

Method Detail

clone

public java.lang.Object clone()

Description copied from interface: IRandom

Returns a clone copy of this instance.

Specified by:

clone in interface IRandom

Specified by:

clone in class BasePRNG

setup

public void setup(java.util.Map attributes)

Specified by:

setup in class BasePRNG

fillBlock

public void fillBlock()
               throws LimitReachedException

Specified by:

fillBlock in class BasePRNG

Throws:

LimitReachedException