gnu.crypto.mac

Class TMMH16

public class TMMH16 extends BaseMac implements Cloneable

TMMH is a universal hash function suitable for message authentication in the Wegman-Carter paradigm, as in the Stream Cipher Security Transform. It is simple, quick, and especially appropriate for Digital Signal Processors and other processors with a fast multiply operation, though a straightforward implementation requires storage equal in length to the largest message to be hashed.

TMMH is a simple hash function which maps a key and a message to a hash value. There are two versions of TMMH: TMMH/16 and TMMH/32. TMMH can be used as a message authentication code, as described in Section 5 (see References).

The key, message, and hash value are all octet strings, and the lengths of these quantities are denoted as KEY_LENGTH, MESSAGE_LENGTH, and TAG_LENGTH, respectively. The values of KEY_LENGTH and TAG_LENGTH MUST be fixed for any particular fixed value of the key, and must obey the alignment restrictions described below.

The parameter MAX_HASH_LENGTH, which denotes the maximum value which MESSAGE_LENGTH may take, is equal to KEY_LENGTH - TAG_LENGTH.

References:

  1. The Truncated Multi-Modular Hash Function (TMMH), David A. McGrew.

Version: $Revision: 1.6 $

Field Summary
static StringKEYSTREAM
static StringPREFIX
static StringTAG_LENGTH
Constructor Summary
TMMH16()
Trivial 0-arguments constructor.
Method Summary
byte[]digest()
byte[]digest(IRandom prng)

Similar to the same method with no arguments, but uses the designated random number generator to compute needed keying material.

voidinit(Map attributes)
intmacSize()
voidreset()
booleanselfTest()
voidupdate(byte b)
voidupdate(byte[] b, int offset, int len)
voidupdate(byte b, IRandom prng)

Similar to the same method with one argument, but uses the designated random number generator to compute needed keying material.

voidupdate(byte[] b, int offset, int len, IRandom prng)

Similar to the same method with three arguments, but uses the designated random number generator to compute needed keying material.

Field Detail

KEYSTREAM

public static final String KEYSTREAM

PREFIX

public static final String PREFIX

TAG_LENGTH

public static final String TAG_LENGTH

Constructor Detail

TMMH16

public TMMH16()
Trivial 0-arguments constructor.

Method Detail

digest

public byte[] digest()

digest

public byte[] digest(IRandom prng)

Similar to the same method with no arguments, but uses the designated random number generator to compute needed keying material.

Parameters: prng the source of randomness to use.

Returns: the final result of the algorithm.

init

public void init(Map attributes)

macSize

public int macSize()

reset

public void reset()

selfTest

public boolean selfTest()

update

public void update(byte b)

update

public void update(byte[] b, int offset, int len)

update

public void update(byte b, IRandom prng)

Similar to the same method with one argument, but uses the designated random number generator to compute needed keying material.

Parameters: b the byte to process. prng the source of randomness to use.

update

public void update(byte[] b, int offset, int len, IRandom prng)

Similar to the same method with three arguments, but uses the designated random number generator to compute needed keying material.

Parameters: b the byte array to process. offset the starting offset in b to start considering the bytes to process. len the number of bytes in b starting from offset to process. prng the source of randomness to use.

Copyright © 2001, 2002, 2003 Free Software Foundation, Inc. All Rights Reserved.