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## cryptix.provider.cipher
Class 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 $

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)

Fields inherited from class java.security.Cipher
`DECRYPT, ENCRYPT, UNINITIALIZED`

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 java.security.Cipher
`blockSize, 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, getClass, hashCode, notify, notifyAll, wait, wait, wait`

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

### getLinkStatus

    public static LinkStatus getLinkStatus()

  Gets an object representing the native linking status of this class.

### finalize

    protected final void finalize()

  Cleans up resources used by this instance, if necessary.
  Overrides:
    finalize in class Object

### 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
  Tags copied from class: Cipher
  Throws:
    CloneNotSupportedException - if the cipher is not cloneable.

### 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(Key key)
                           throws InvalidKeyException

  SPI: Initializes this cipher for encryption, using the specified key.
  Overrides:
    engineInitEncrypt in class Cipher
  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.

### engineInitDecrypt

    public void engineInitDecrypt(Key key)
                           throws InvalidKeyException,
                                  CryptixException

  SPI: Initializes this cipher for decryption, using the specified key.
  Overrides:
    engineInitDecrypt in class Cipher
  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.

### 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 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.

### 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

### 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.

### main

    public static void main(String[] argv)

  Entry point for `self_test`.

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Copyright (C) 1995-2000 The Cryptix Foundation Ltd. All rights reserved.