gnu.crypto.mac
Class BaseMac

java.lang.Object
  gnu.crypto.mac.BaseMac

All Implemented Interfaces:

java.lang.Cloneable, IMac

Direct Known Subclasses:

HMac, TMMH16, UHash32, UMac32

public abstract class BaseMac

extends java.lang.Object

implements IMac

A base abstract class to facilitate MAC (Message Authentication Code) implementations.

Version:

$Revision: 1.2 $

Field Summary

protected java.lang.String	name The canonical name prefix of the MAC.
protected int	truncatedSize The length of the truncated output in bytes.
protected IMessageDigest	underlyingHash Reference to the underlying hash algorithm instance.

Fields inherited from interface gnu.crypto.mac.IMac

MAC_KEY_MATERIAL, TRUNCATED_SIZE

Constructor Summary

protected	BaseMac(java.lang.String name) Trivial constructor for use by concrete subclasses.
protected	BaseMac(java.lang.String name, IMessageDigest underlyingHash) Trivial constructor for use by concrete subclasses.

Method Summary

abstract java.lang.Object	clone() Returns a clone copy of this instance.
abstract byte[]	digest() Completes the MAC by performing final operations such as padding and resetting the instance.
abstract void	init(java.util.Map attributes) Initialises the algorithm with designated attributes.
int	macSize() Returns the output length in bytes of this MAC algorithm.
java.lang.String	name() Returns the canonical name of this algorithm.
void	reset() Resets the algorithm instance for re-initialisation and use with other characteristics.
abstract boolean	selfTest() A basic test.
void	update(byte b) Continues a MAC operation using the input byte.
void	update(byte[] b, int offset, int len) Continues a MAC operation, by filling the buffer, processing data in the algorithm's MAC_SIZE-bit block(s), updating the context and count, and buffering the remaining bytes in buffer for the next operation.

Methods inherited from class java.lang.Object

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

Field Detail

name

protected java.lang.String name

The canonical name prefix of the MAC.

underlyingHash

protected IMessageDigest underlyingHash

Reference to the underlying hash algorithm instance.

truncatedSize

protected int truncatedSize

The length of the truncated output in bytes.

Constructor Detail

BaseMac

protected BaseMac(java.lang.String name)

Trivial constructor for use by concrete subclasses.

Parameters:

name - the canonical name of this instance.

BaseMac

protected BaseMac(java.lang.String name,
                  IMessageDigest underlyingHash)

Trivial constructor for use by concrete subclasses.

Parameters:

name - the canonical name of this instance.

underlyingHash - the underlying message digest algorithm instance.

Method Detail

name

public java.lang.String name()

Description copied from interface: IMac

Returns the canonical name of this algorithm.

Specified by:

name in interface IMac

Returns:

the canonical name of this algorithm.

macSize

public int macSize()

Description copied from interface: IMac

Returns the output length in bytes of this MAC algorithm.

Specified by:

macSize in interface IMac

Returns:

the output length in bytes of this MAC algorithm.

update

public void update(byte b)

Description copied from interface: IMac

Continues a MAC operation using the input byte.

Specified by:

update in interface IMac

Parameters:

b - the input byte to digest.

update

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

Description copied from interface: IMac

Continues a MAC operation, by filling the buffer, processing data in the algorithm's MAC_SIZE-bit block(s), updating the context and count, and buffering the remaining bytes in buffer for the next operation.

Specified by:

update in interface IMac

Parameters:

b - the input block.

offset - start of meaningful bytes in input block.

len - number of bytes, in input block, to consider.

reset

public void reset()

Description copied from interface: IMac

Resets the algorithm instance for re-initialisation and use with other characteristics. This method always succeeds.

Specified by:

reset in interface IMac

clone

public abstract java.lang.Object clone()

Description copied from interface: IMac

Returns a clone copy of this instance.

Specified by:

clone in interface IMac

init

public abstract void init(java.util.Map attributes)
                   throws java.security.InvalidKeyException,
                          java.lang.IllegalStateException

Description copied from interface: IMac

Initialises the algorithm with designated attributes. Permissible names and values are described in the class documentation above.

Specified by:

init in interface IMac

Parameters:

attributes - a set of name-value pairs that describe the desired future instance behaviour.

Throws:

java.security.InvalidKeyException - if the key data is invalid.

java.lang.IllegalStateException - if the instance is already initialised.

See Also:

IMac.MAC_KEY_MATERIAL

digest

public abstract byte[] digest()

Description copied from interface: IMac

Completes the MAC by performing final operations such as padding and resetting the instance.

Specified by:

digest in interface IMac

Returns:

the array of bytes representing the MAC value.

selfTest

public abstract boolean selfTest()

Description copied from interface: IMac

A basic test. Ensures that the MAC of a pre-determined message is equal to a known pre-computed value.

Specified by:

selfTest in interface IMac

Returns:

true if the implementation passes a basic self-test. Returns false otherwise.