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

Fields inherited from class xjava.security.PaddingScheme
blockSize
 
Fields inherited from class xjava.security.IJCE_Traceable
tracing
 
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 xjava.security.IJCE_Traceable
, disableTracing, enableTracing, traceMethod, traceResult, traceResult, traceVoidMethod
 
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].
Overrides:
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.

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.

Overrides:
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