cryptix.provider.cipher

Class DES

Implemented Interfaces:
Parameterized, SymmetricCipher

public final class DES
extends Cipher
implements SymmetricCipher

DES is a block cipher with an 8 byte block size. The key length is 8 bytes, but only 56 bits are used as the parity bit in each byte is ignored.

This algorithm has been seriously analysed over the last 30 years, and no significant weaknesses have been reported. Its only known flaw is that the key length of 56 bits makes it relatively easy to brute-force it.

To overcome this near-fatal flaw, it is recommended that DES be used in Triple DES mode. The JCA algorithm name for the recommended form of Triple DES is "DES-EDE3/CBC", which is implemented by the DES_EDE3 and CBC

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," Applied Cryptography, 2nd edition, John Wiley & Sons, 1996.

  2. NIST FIPS PUB 46-2 (supercedes FIPS PUB 46-1), "Data Encryption Standard", U.S. Department of Commerce, December 1993.
    http://www.itl.nist.gov/div897/pubs/fip46-2.htm

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

$Revision: 1.6 $

Authors:
Systemics Ltd
Geoffrey Keating (this Java implementation)
Eric Young
David Hopwood
Raif S. Naffah
John F. Dumas (jdumas@zgs.com)
Since:
Cryptix 2.2.2

Field Summary

Fields inherited from class xjava.security.Cipher

DECRYPT, ENCRYPT, UNINITIALIZED

Fields inherited from class xjava.security.IJCE_Traceable

tracing

Constructor Summary

DES()
Constructs a DES cipher object, in the UNINITIALIZED state.

Method Summary

Object
clone()
Always throws a CloneNotSupportedException (cloning of ciphers is not supported for security reasons).
int[]
crypt3(int E0, int E1)
Implements the Unix crypt(3) algorithm.
protected void
des(byte[] in, int inOffset, byte[] out, int outOffset, boolean encrypt)
Encrypts/decrypts a block, of length BLOCK_SIZE.
int
engineBlockSize()
SPI: Returns the length of an input block, in bytes.
void
engineInitDecrypt(Key key)
SPI: Initializes this cipher for decryption, using the specified key.
void
engineInitEncrypt(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.
protected void
finalize()
Cleans up resources used by this instance, if necessary.
static LinkStatus
getLinkStatus()
Gets an object representing the native linking status of this class.
static void
main(String[] argv)
Entry point for self_test.

Methods inherited from class xjava.security.Cipher

blockSize, clone, crypt, crypt, crypt, doFinal, doFinal, doFinal, doFinal, engineBlockSize, engineCiphertextBlockSize, engineCrypt, engineGetParameter, engineInBufferSize, engineInitDecrypt, engineInitEncrypt, engineOutBufferSize, enginePlaintextBlockSize, engineSetPaddingScheme, engineSetParameter, engineUpdate, 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 xjava.security.IJCE_Traceable

disableTracing, enableTracing, traceMethod, traceResult, traceResult, traceVoidMethod

Constructor Details

DES

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

Method Details

clone

public final Object clone()
            throws CloneNotSupportedException
Always throws a CloneNotSupportedException (cloning of ciphers is not supported for security reasons).
Overrides:
clone in interface Cipher

crypt3

public int[] crypt3(int E0,
                    int E1)
Parameters:
E0 - first 32 bits of input.
E1 - second 32 bits of input.

des

protected void des(byte[] in,
                   int inOffset,
                   byte[] out,
                   int outOffset,
                   boolean encrypt)
Encrypts/decrypts a block, of length BLOCK_SIZE.
Parameters:
in - an array containing the input block
inOffset - the starting offset of the input block
out - an array containing the output block
encrypt - true to encrypt, false to decrypt

engineBlockSize

public int engineBlockSize()
SPI: Returns the length of an input block, in bytes.
Overrides:
engineBlockSize in interface Cipher
Returns:
the length in bytes of an input block for this cipher.

engineInitDecrypt

public void engineInitDecrypt(Key key)
            throws InvalidKeyException,
                   CryptixException
SPI: Initializes this cipher for decryption, using the specified key.
Overrides:
engineInitDecrypt in interface Cipher
Parameters:
key - the key to use for decryption.

engineInitEncrypt

public void engineInitEncrypt(Key key)
            throws InvalidKeyException
SPI: Initializes this cipher for encryption, using the specified key.
Overrides:
engineInitEncrypt in interface Cipher
Parameters:
key - the key to use for encryption.

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.

Overrides:
engineUpdate in interface 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.

finalize

protected final void finalize()
Cleans up resources used by this instance, if necessary.

getLinkStatus

public static LinkStatus getLinkStatus()
Gets an object representing the native linking status of this class.

main

public static void main(String[] argv)
Entry point for self_test.