cryptix.provider.padding
Class PKCS5

java.lang.Object
  xjava.security.IJCE_Traceable
      xjava.security.PaddingScheme
          cryptix.provider.padding.PKCS5

All Implemented Interfaces:

Padding, Parameterized

public class PKCS5

extends PaddingScheme

A class for padding cipher data according to the following scheme, described in section 6.2 of RSA Data Security, Inc.'s PKCS #5 standard:

    ...
 

An IllegalBlockSizeException is thrown (by the Cipher class) if the block size is not 8 bytes.

References:

1. PKCS#5: ... An RSA Laboratories Technical Note; Version 1.5; Revised November 1, 1993.

Copyright © 1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.7 $

Since:

Cryptix 2.2.2

Author:

Raif S. Naffah, David Hopwood

Field Summary

Fields inherited from class xjava.security.PaddingScheme

blockSize

Constructor Summary

PKCS5()
Creates a PKCS5 object.

Method Summary

protected boolean	engineIsValidBlockSize(int size) SPI: Returns true if size is a valid block size (in bytes) for this algorithm.
protected int	enginePad(byte[] in, int offset, int length) Pads a given array of bytes.
protected int	engineUnpad(byte[] in, int offset, int length) Given the specified subarray of bytes that includes padding bytes, returns the index indicating where padding starts.

Methods inherited from class xjava.security.PaddingScheme

clone, engineGetParameter, engineSetBlockSize, engineSetParameter, getAlgorithm, getAlgorithms, getAlgorithms, getBlockSize, getInstance, getInstance, getParameter, pad, paddingScheme, padLength, setParameter, toString, unpad

Methods inherited from class java.lang.Object

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

Constructor Detail

PKCS5

public PKCS5()

Creates a PKCS5 object.

Method Detail

enginePad

protected int enginePad(byte[] in,
                        int offset,
                        int length)

Pads a given array of bytes. The padding is written to the same buffer that is used for input (in). When this method returns, the padded block will be stored at in[offset+length..offset+7].

Specified by:

enginePad in class PaddingScheme

Parameters:

in - the buffer containing the incomplete block.

offset - the offset into the in buffer of the first byte in the group of bytes to be padded.

length - the number of bytes from the in buffer, starting at offset, that need to be padded.

Returns:

the number of padding bytes written.

engineUnpad

protected int engineUnpad(byte[] in,
                          int offset,
                          int length)

Given the specified subarray of bytes that includes padding bytes, returns the index indicating where padding starts.

For PKCS#5, the padding bytes all have value 8 - (length % 8). Hence to find the number of added bytes, it's enough to consider the last byte value of the padded message.

Specified by:

engineUnpad in class PaddingScheme

Parameters:

in - the buffer containing the bytes.

offset - the offset into the in buffer of the first byte in the block.

length - the length of the block in bytes.

Returns:

the index into the in buffer indicating where the padding starts.

Throws:

CryptixException - if the number of padding bytes is invalid.

engineIsValidBlockSize

protected boolean engineIsValidBlockSize(int size)

SPI: Returns true if size is a valid block size (in bytes) for this algorithm.

For PKCS#5 padding, the only valid size is 8 bytes.

Overrides:

engineIsValidBlockSize in class PaddingScheme