cryptix.provider.cipher

Class DESX

public class DESX extends Cipher implements SymmetricCipher

This class implements DESX encryption with two independent keys. DESX acts as a block cipher with an 8 byte block size.

The encoded form of the DESX key should be a 24-byte array, consisting of one 8-byte DES key K and two XOR keys K1 and K2 in order - K, K1 and K2. Encryption and decryption are done as follows:

When DESX is used with the CBC mode class (algorithm name "DESX/CBC"), the result is Outer-CBC, and only one IV is used.

References:

  1. Bruce Schneier, "Chapter 12 Data Encryption Standard," and "Section 15.2 Triple Encryption," Applied Cryptography, 2nd edition, John Wiley & Sons, 1996

  2. R.C. Merkle and M. Hellman, "On the Security of Multiple Encryption," Communications of the ACM, vol. 24 no. 7, 1981, pages 465-467.

  3. P Karn, P Metzger, W A Simpson "The ESP Triple DES Transform," Internet Draft, draft-simpson-esp-des3-x-01.txt

Copyright © 1998 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.3 $

Since: Cryptix 3.0.4

Author: Sascha Kettler

Constructor Summary
DESX()
Constructs a DESX cipher object, in the UNINITIALIZED state.
Method Summary
intengineBlockSize()
SPI: Returns the length of an input block, in bytes.
protected voidengineInitDecrypt(Key key)
SPI: Initializes this cipher for decryption, using the specified key.
voidengineInitEncrypt(Key key)
SPI: Initializes this cipher for encryption, using the specified key.
protected intengineUpdate(byte[] in, int inOffset, int inLen, byte[] out, int outOffset)
SPI: This is the main engine method for updating data.

Constructor Detail

DESX

public DESX()
Constructs a DESX cipher object, in the UNINITIALIZED state. This calls the Cipher constructor with implBuffering false, implPadding false and the provider set to "Cryptix".

Method Detail

engineBlockSize

public int engineBlockSize()
SPI: Returns the length of an input block, in bytes.

Returns: the length in bytes of an input block for this cipher.

engineInitDecrypt

protected void engineInitDecrypt(Key key)
SPI: Initializes this cipher for decryption, using the specified key.

Parameters: key the key to use for decryption.

Throws: KeyException if one of the following occurs:

engineInitEncrypt

public void engineInitEncrypt(Key key)
SPI: Initializes this cipher for encryption, using the specified key.

Parameters: key the key to use for encryption.

Throws: KeyException if one of the following occurs:

engineUpdate

protected int engineUpdate(byte[] in, int inOffset, int inLen, byte[] out, int outOffset)
SPI: This is the main engine method for updating data.

in and out may be the same array, and the input and output regions may overlap.

Parameters: in the input data. inOffset the offset into in specifying where the data starts. inLen the length of the subarray. out the output array. outOffset the offset indicating where to start writing into the out array.

Returns: the number of bytes written.

Throws: CryptixException if the native library is being used, and it reports an error.