gnu.crypto.pad
Class BasePad

java.lang.Object
  gnu.crypto.pad.BasePad

All Implemented Interfaces:

IPad

Direct Known Subclasses:

PKCS1_V1_5, PKCS7, TBC

public abstract class BasePad

extends java.lang.Object

implements IPad

An abstract class to facilitate implementing padding algorithms.

Version:

$Revision: 1.2 $

Field Summary

protected int	blockSize The block size, in bytes, for this instance.
protected java.lang.String	name The canonical name prefix of the padding algorithm.

Constructor Summary

protected

BasePad(java.lang.String name) Trivial constructor for use by concrete subclasses.

Method Summary

void	init(int bs) Initialises the padding scheme with a designated block size.
java.lang.String	name()
abstract byte[]	pad(byte[] in, int off, int len) Returns the byte sequence that should be appended to the designated input.
void	reset() Resets the scheme instance for re-initialisation and use with other characteristics.
boolean	selfTest() A basic symmetric pad/unpad test.
abstract void	setup() If any additional checks or resource setup must be done by the subclass, then this is the hook for it.
abstract int	unpad(byte[] in, int off, int len) Returns the number of bytes to discard from a designated input buffer.

Methods inherited from class java.lang.Object

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

Field Detail

name

protected java.lang.String name

The canonical name prefix of the padding algorithm.

blockSize

protected int blockSize

The block size, in bytes, for this instance.

Constructor Detail

BasePad

protected BasePad(java.lang.String name)

Trivial constructor for use by concrete subclasses.

Method Detail

name

public java.lang.String name()

Specified by:

name in interface IPad

Returns:

the canonical name of this instance.

init

public void init(int bs)
          throws java.lang.IllegalStateException

Description copied from interface: IPad

Initialises the padding scheme with a designated block size.

Specified by:

init in interface IPad

Parameters:

bs - the designated block size.

Throws:

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

reset

public void reset()

Description copied from interface: IPad

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

Specified by:

reset in interface IPad

selfTest

public boolean selfTest()

Description copied from interface: IPad

A basic symmetric pad/unpad test.

Specified by:

selfTest in interface IPad

Returns:

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

setup

public abstract void setup()

If any additional checks or resource setup must be done by the subclass, then this is the hook for it. This method will be called before the init(int) method returns.

pad

public abstract byte[] pad(byte[] in,
                           int off,
                           int len)

Description copied from interface: IPad

Returns the byte sequence that should be appended to the designated input.

Specified by:

pad in interface IPad

Parameters:

in - the input buffer containing the bytes to pad.

off - the starting index of meaningful data in in.

len - the number of meaningful bytes in in.

Returns:

the possibly 0-byte long sequence to be appended to the designated input.

unpad

public abstract int unpad(byte[] in,
                          int off,
                          int len)
                   throws WrongPaddingException

Description copied from interface: IPad

Returns the number of bytes to discard from a designated input buffer.

Specified by:

unpad in interface IPad

Parameters:

in - the input buffer containing the bytes to unpad.

off - the starting index of meaningful data in in.

len - the number of meaningful bytes in in.

Returns:

the number of bytes to discard, to the left of index position offset + length in in. In other words, if the return value of a successful invocation of this method is result, then the unpadded byte sequence will be offset + length - result bytes in in, starting from index position offset.

Throws:

WrongPaddingException - if the data is not terminated with the expected padding bytes.