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gnu.javax.crypto.pad

Interface IPad

Known Implementing Classes:
BasePad, ISO10126, PKCS1_V1_5, PKCS7, SSL3, TBC, TLS1
public interface IPad
The basic visible methods, and attribute names, of every padding algorithm.

Padding algorithms serve to pad and unpad byte arrays usually as the last step in an encryption or respectively a decryption operation. Their input buffers are usually those processed by instances of IMode and/or IBlockCipher.

Field Summary

static String
PADDING_BLOCK_SIZE
Property name of the block size in which to operate the padding algorithm.

Method Summary

void
init(int bs)
Initialises the padding scheme with a designated block size.
void
init(Map<K,V> attributes)
Initialises the algorithm with designated attributes.
String
name()
byte[]
pad(byte[] in, int offset, int length)
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.
int
unpad(byte[] in, int offset, int length)
Returns the number of bytes to discard from a designated input buffer.

Field Details

PADDING_BLOCK_SIZE

public static final String PADDING_BLOCK_SIZE
Property name of the block size in which to operate the padding algorithm. The value associated with this property name is taken to be a positive Integer greater than zero.
Field Value:
"gnu.crypto.pad.block.size"

Method Details

init

public void init(int bs)
            throws IllegalStateException
Initialises the padding scheme with a designated block size.
Parameters:
bs - the designated block size.
Throws:
IllegalStateException - if the instance is already initialised.
IllegalArgumentException - if the block size value is invalid.

init

public void init(Map<K,V> attributes)
            throws IllegalStateException
Initialises the algorithm with designated attributes. Names, valid and/or recognisable by all concrete implementations are described in the class documentation above. Other algorithm-specific attributes MUST be documented in the implementation class of that padding algorithm.
Parameters:
attributes - a set of name-value pairs that describes the desired future behaviour of this instance.
Throws:
IllegalStateException - if the instance is already initialised.
IllegalArgumentException - if the block size value is invalid.

name

public String name()
Returns:
the canonical name of this instance.

pad

public byte[] pad(byte[] in,
                  int offset,
                  int length)
Returns the byte sequence that should be appended to the designated input.
Parameters:
in - the input buffer containing the bytes to pad.
offset - the starting index of meaningful data in in.
length - the number of meaningful bytes in in.
Returns:
the possibly 0-byte long sequence to be appended to the designated input.

reset

public void reset()
Resets the scheme instance for re-initialisation and use with other characteristics. This method always succeeds.

selfTest

public boolean selfTest()
A basic symmetric pad/unpad test.
Returns:
true if the implementation passes a basic symmetric self-test. Returns false otherwise.

unpad

public int unpad(byte[] in,
                 int offset,
                 int length)
            throws WrongPaddingException
Returns the number of bytes to discard from a designated input buffer.
Parameters:
in - the input buffer containing the bytes to unpad.
offset - the starting index of meaningful data in in.
length - 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.
IPad.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.

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