cryptix.provider.cipher

Class DES_EDE3

java.lang.Object

xjava.security.IJCE_Traceable

xjava.security.Cipher

cryptix.provider.cipher.DES_EDE3

All Implemented Interfaces:

Parameterized, SymmetricCipher

public class DES_EDE3
extends Cipher
implements SymmetricCipher

This class implements Triple DES EDE encryption with three independent keys. DES-EDE3 acts as a block cipher with an 8 byte block size.

The encoded form of the Triple DES key should be a 24-byte array, consisting of three 8-byte single DES keys in order - K1, K2 and K3. Encryption and decryption are done as follows:

• C = E_K3(D_K2(E_K1(P)))
• P = D_K1(E_K2(D_K3(C)))

The alternating encryption and decryption was designed by IBM to enable compatibility with single DES, when all three keys are equal (although it is now rare for Triple DES to be used in that way).

When DES-EDE3 is used with the CBC mode class (algorithm name "DES-EDE3/CBC"), the result is Outer-CBC, and only one IV is used.

DES was written by IBM and first released in 1976. The algorithm is freely usable for both single and triple encryption.

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

$Revision: 1.6 $

Since:

Cryptix 2.2.2

Author:

David Hopwood

Field Summary

Fields inherited from class xjava.security.Cipher

DECRYPT, ENCRYPT, UNINITIALIZED

Constructor Summary

Constructors

Constructor and Description
DES_EDE3() Constructs a DES-EDE3 cipher object, in the UNINITIALIZED state.

Method Summary

Methods

Modifier and Type	Method and Description
int	engineBlockSize() SPI: Returns the length of an input block, in bytes.
protected void	engineInitDecrypt(java.security.Key key) SPI: Initializes this cipher for decryption, using the specified key.
void	engineInitEncrypt(java.security.Key key) SPI: Initializes this cipher for encryption, using the specified key.
protected int	engineUpdate(byte[] in, int inOffset, int inLen, byte[] out, int outOffset) SPI: This is the main engine method for updating data.

Methods inherited from class xjava.security.Cipher

blockSize, clone, crypt, crypt, crypt, doFinal, doFinal, doFinal, doFinal, engineCiphertextBlockSize, engineCrypt, engineGetParameter, engineInBufferSize, engineOutBufferSize, enginePlaintextBlockSize, engineSetPaddingScheme, engineSetParameter, getAlgorithm, getAlgorithms, getAlgorithms, getCiphertextBlockSize, getInputBlockSize, getInstance, getInstance, getInstance, getMode, getOutputBlockSize, getPadding, getPaddingScheme, getParameter, getPlaintextBlockSize, getProvider, getState, inBufferSize, inBufferSizeFinal, initDecrypt, initEncrypt, isPaddingBlockCipher, outBufferSize, outBufferSizeFinal, setParameter, toString, update, update, update, update

Methods inherited from class java.lang.Object

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

Constructor Detail

DES_EDE3

public DES_EDE3()

Constructs a DES-EDE3 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.

Overrides:

engineBlockSize in class Cipher

Returns:

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

engineInitEncrypt

public void engineInitEncrypt(java.security.Key key)
                       throws java.security.KeyException

SPI: Initializes this cipher for encryption, using the specified key.

Specified by:

engineInitEncrypt in class Cipher

Parameters:

key - the key to use for encryption.

Throws:

java.security.KeyException - if one of the following occurs:

• key.getEncoded() == null;
• The length of the user key array is invalid.

engineInitDecrypt

protected void engineInitDecrypt(java.security.Key key)
                          throws java.security.KeyException

SPI: Initializes this cipher for decryption, using the specified key.

Specified by:

engineInitDecrypt in class Cipher

Parameters:

key - the key to use for decryption.

Throws:

java.security.KeyException - if one of the following occurs:

• key.getEncoded() == null;
• The length of the user key array is invalid.

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.

Specified by:

engineUpdate in class Cipher

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.