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Class cryptix.provider.cipher.DES

java.lang.Object
   |
   +----java.security.IJCE_Traceable
           |
           +----java.security.Cipher
                   |
                   +----cryptix.provider.cipher.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: 1.5 $

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

Constructor Index

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

Method Index

 o clone()
Always throws a CloneNotSupportedException (cloning of ciphers is not supported for security reasons).
 o crypt3(int, int)
Implements the Unix crypt(3) algorithm.
 o des(byte[], int, byte[], int, boolean)
Encrypts/decrypts a block, of length BLOCK_SIZE.
 o engineBlockSize()
SPI: Returns the length of an input block, in bytes.
 o engineInitDecrypt(Key)
SPI: Initializes this cipher for decryption, using the specified key.
 o engineInitEncrypt(Key)
SPI: Initializes this cipher for encryption, using the specified key.
 o engineUpdate(byte[], int, int, byte[], int)
SPI: This is the main engine method for updating data.
 o finalize()
Cleans up resources used by this instance, if necessary.
 o getLinkStatus()
Gets an object representing the native linking status of this class.
 o main(String[])
Entry point for self_test.

Constructors

 o 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".

Methods

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

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

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

Overrides:
clone in class Cipher
 o 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.
Overrides:
engineBlockSize in class Cipher
 o engineInitEncrypt
 public void engineInitEncrypt(Key key) throws InvalidKeyException
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:
  • key.getEncoded() == null;
  • The length of the user key array is not KEY_LENGTH.
Overrides:
engineInitEncrypt in class Cipher
 o engineInitDecrypt
 public void engineInitDecrypt(Key key) throws InvalidKeyException, CryptixException
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:
  • key.getEncoded() == null;
  • The length of the user key array is not KEY_LENGTH.
Overrides:
engineInitDecrypt in class Cipher
 o 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.
Overrides:
engineUpdate in class Cipher
 o 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
 o 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.
 o main
 public static void main(String argv[])
Entry point for self_test.


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