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Class UMacGenerator  view UMacGenerator download

      extended bygnu.javax.crypto.prng.UMacGenerator
All Implemented Interfaces:

public class UMacGenerator
implements java.lang.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 java.lang.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 taken to be an instance of java.lang.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 java.lang.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.


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

Field Summary
private  gnu.javax.crypto.cipher.IBlockCipher cipher
          The generator's underlying block cipher.
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
buffer, initialised, name, ndx
Constructor Summary
          Trivial 0-arguments constructor.
Method Summary
 void fillBlock()
 void setup(java.util.Map attributes)
Methods inherited from class
addRandomByte, addRandomBytes, addRandomBytes, clone, init, isInitialised, name, nextByte, nextBytes, nextBytes
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail


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 java.lang.Integer less than 256.

See Also:
Constant Field Values


public static final java.lang.String CIPHER
The name of the underlying symmetric key block cipher algorithm.

See Also:
Constant Field Values


private gnu.javax.crypto.cipher.IBlockCipher cipher
The generator's underlying block cipher.

Constructor Detail


public UMacGenerator()
Trivial 0-arguments constructor.

Method Detail


public void setup(java.util.Map attributes)


public void fillBlock()