gnu.crypto.mac

Class TMMH16

Implemented Interfaces:
Cloneable, IMac

public class TMMH16
extends BaseMac

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: 1.4 $

Field Summary

static String
KEYSTREAM
static String
PREFIX
static String
TAG_LENGTH

Fields inherited from class gnu.crypto.mac.BaseMac

name, truncatedSize, underlyingHash

Fields inherited from interface gnu.crypto.mac.IMac

MAC_KEY_MATERIAL, TRUNCATED_SIZE

Constructor Summary

TMMH16()
Trivial 0-arguments constructor.

Method Summary

Object
clone()
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.
void
init(Map attributes)
int
macSize()
void
reset()
boolean
selfTest()
void
update(byte b)
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.
void
update(byte[] b, int offset, int len)
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.

Methods inherited from class gnu.crypto.mac.BaseMac

clone, digest, init, macSize, name, reset, selfTest, update, update

Field Details

KEYSTREAM

public static final String KEYSTREAM


PREFIX

public static final String PREFIX


TAG_LENGTH

public static final String TAG_LENGTH

Constructor Details

TMMH16

public TMMH16()
Trivial 0-arguments constructor.

Method Details

clone

public Object clone()
Specified by:
clone in interface IMac
Overrides:
clone in interface BaseMac


digest

public byte[] digest()
Specified by:
digest in interface IMac
Overrides:
digest in interface BaseMac


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)
            throws InvalidKeyException,
                   IllegalStateException
Specified by:
init in interface IMac
Overrides:
init in interface BaseMac


macSize

public int macSize()
Specified by:
macSize in interface IMac
Overrides:
macSize in interface BaseMac


reset

public void reset()
Specified by:
reset in interface IMac
Overrides:
reset in interface BaseMac


selfTest

public boolean selfTest()
Specified by:
selfTest in interface IMac
Overrides:
selfTest in interface BaseMac


update

public void update(byte b)
Specified by:
update in interface IMac
Overrides:
update in interface BaseMac


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)
Specified by:
update in interface IMac
Overrides:
update in interface BaseMac


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.