gnu.javax.crypto.mac

Class BaseMac

Implemented Interfaces:
IMac
Known Direct Subclasses:
HMac, TMMH16, UHash32, UMac32

public abstract class BaseMac
extends Object
implements IMac

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

Field Summary

protected 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.javax.crypto.mac.IMac

MAC_KEY_MATERIAL, TRUNCATED_SIZE

Constructor Summary

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

Method Summary

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(Map<K,V> attributes)
Initialises the algorithm with designated attributes.
int
macSize()
Returns the output length in bytes of this MAC algorithm.
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

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

name

protected String name
The canonical name prefix of the MAC.

truncatedSize

protected int truncatedSize
The length of the truncated output in bytes.

underlyingHash

protected IMessageDigest underlyingHash
Reference to the underlying hash algorithm instance.

Constructor Details

BaseMac

protected BaseMac(String name)
Trivial constructor for use by concrete subclasses.
Parameters:
name - the canonical name of this instance.

BaseMac

protected BaseMac(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 Details

clone

public Object clone()
            throws CloneNotSupportedException
Returns a clone copy of this instance.
Specified by:
clone in interface IMac
Overrides:
clone in interface Object
Returns:
a clone copy of this instance.

digest

public abstract byte[] digest()
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.

init

public abstract void init(Map<K,V> attributes)
            throws InvalidKeyException,
                   IllegalStateException
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:
InvalidKeyException - if the key data is invalid.
IllegalStateException - if the instance is already initialised.

macSize

public int macSize()
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.

name

public String name()
Returns the canonical name of this algorithm.
Specified by:
name in interface IMac
Returns:
the canonical name of this algorithm.

reset

public void reset()
Resets the algorithm instance for re-initialisation and use with other characteristics. This method always succeeds.
Specified by:
reset in interface IMac

selfTest

public abstract boolean selfTest()
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.

update

public void update(byte b)
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)
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:
offset - start of meaningful bytes in input block.

BaseMac.java -- Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc. This file is a part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.