cryptix.provider.cipher

Class DES

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 $

Since: Cryptix 2.2.2

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

Constructor Summary
DES()
Constructs a DES cipher object, in the UNINITIALIZED state.
Method Summary
Objectclone()
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 voiddes(byte[] in, int inOffset, byte[] out, int outOffset, boolean encrypt)
Encrypts/decrypts a block, of length BLOCK_SIZE.
intengineBlockSize()
SPI: Returns the length of an input block, in bytes.
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.
protected voidfinalize()
Cleans up resources used by this instance, if necessary.
static LinkStatusgetLinkStatus()
Gets an object representing the native linking status of this class.
static voidmain(String[] argv)
Entry point for self_test.

Constructor Detail

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 Detail

clone

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

crypt3

public int[] crypt3(int E0, int E1)
Implements the Unix crypt(3) algorithm.

This method is intended only for use by the class cryptix.tools.UnixCrypt, and should not be used directly by applications.

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 inOffset the starting offset of the output block encrypt true to encrypt, false to decrypt

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

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

Parameters: key the key to use for decryption.

Throws: InvalidKeyException 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: InvalidKeyException 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.

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.