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gnu.javax.crypto.cipher

Class DES

Implemented Interfaces:
Cloneable, IBlockCipher, gnu.javax.crypto.cipher.IBlockCipherSpi
public class DES
extends BaseCipher
The Data Encryption Standard. DES is a 64-bit block cipher with a 56-bit key, developed by IBM in the 1970's for the standardization process begun by the National Bureau of Standards (now NIST).

New applications should not use DES except for compatibility.

This version is based upon the description and sample implementation in [1].

References:

  1. Bruce Schneier, Applied Cryptography: Protocols, Algorithms, and Source Code in C, Second Edition. (1996 John Wiley and Sons) ISBN 0-471-11709-9. Pages 265--301, 623--632.

Field Summary

static int
BLOCK_SIZE
DES operates on 64 bit blocks.
static int
KEY_SIZE
DES uses 56 bits of a 64 bit parity-adjusted key.
static byte[][]
POSSIBLE_WEAK_KEYS
Possible weak keys (parity adjusted) --produce 4 instead of 16 subkeys.
static byte[][]
SEMIWEAK_KEYS
Semi-weak keys (parity adjusted): Some pairs of keys encrypt plain text to identical cipher text.
static byte[][]
WEAK_KEYS
Weak keys (parity adjusted): If all the bits in each half are either 0 or 1, then the key used for any cycle of the algorithm is the same as all other cycles.

Fields inherited from class gnu.javax.crypto.cipher.BaseCipher

currentBlockSize, currentKey, defaultBlockSize, defaultKeySize, lock, name

Fields inherited from interface gnu.javax.crypto.cipher.IBlockCipher

CIPHER_BLOCK_SIZE, KEY_MATERIAL

Constructor Summary

DES()
Default 0-argument constructor.

Method Summary

static void
adjustParity(byte[] kb, int offset)
Adjust the parity for a raw key array.
Iterator<E>
blockSizes()
Returns an Iterator over the supported block sizes.
Object
clone()
Returns a clone of this instance.
void
decrypt(byte[] in, int i, byte[] out, int o, Object K, int bs)
void
encrypt(byte[] in, int i, byte[] out, int o, Object K, int bs)
static boolean
isParityAdjusted(byte[] kb, int offset)
Test if a byte array, which must be at least 8 bytes long, is parity adjusted.
static boolean
isPossibleWeak(byte[] kb)
Test if the designated byte array represents a possibly weak key.
static boolean
isSemiWeak(byte[] kb)
Test if a key is a semi-weak key.
static boolean
isWeak(byte[] kb)
Test if a key is a weak key.
Iterator<E>
keySizes()
Returns an Iterator over the supported key sizes.
Object
makeKey(byte[] kb, int bs)

Methods inherited from class gnu.javax.crypto.cipher.BaseCipher

clone, currentBlockSize, decryptBlock, defaultBlockSize, defaultKeySize, encryptBlock, init, name, reset, selfTest, testKat, testKat

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

BLOCK_SIZE

public static final int BLOCK_SIZE
DES operates on 64 bit blocks.
Field Value:
8

KEY_SIZE

public static final int KEY_SIZE
DES uses 56 bits of a 64 bit parity-adjusted key.
Field Value:
8

POSSIBLE_WEAK_KEYS

public static final byte[][] POSSIBLE_WEAK_KEYS
Possible weak keys (parity adjusted) --produce 4 instead of 16 subkeys.

SEMIWEAK_KEYS

public static final byte[][] SEMIWEAK_KEYS
Semi-weak keys (parity adjusted): Some pairs of keys encrypt plain text to identical cipher text. In other words, one key in the pair can decrypt messages that were encrypted with the other key. These keys are called semi-weak keys. This occurs because instead of 16 different sub-keys being generated, these semi-weak keys produce only two different sub-keys.

WEAK_KEYS

public static final byte[][] WEAK_KEYS
Weak keys (parity adjusted): If all the bits in each half are either 0 or 1, then the key used for any cycle of the algorithm is the same as all other cycles.

Constructor Details

DES

public DES()
Default 0-argument constructor.

Method Details

adjustParity

public static void adjustParity(byte[] kb,
                                int offset)
Adjust the parity for a raw key array. This essentially means that each byte in the array will have an odd number of '1' bits (the last bit in each byte is unused.
Parameters:
kb - The key array, to be parity-adjusted.
offset - The starting index into the key bytes.

blockSizes

public Iterator<E> blockSizes()
Returns an Iterator over the supported block sizes. Each element returned by this object is an Integer.
Specified by:
blockSizes in interface IBlockCipher
blockSizes in interface gnu.javax.crypto.cipher.IBlockCipherSpi
Returns:
an Iterator over the supported block sizes.

clone

public Object clone()
Returns a clone of this instance.
Specified by:
clone in interface IBlockCipher
Overrides:
clone in interface BaseCipher
Returns:
a clone copy of this instance.

decrypt

public void decrypt(byte[] in,
                    int i,
                    byte[] out,
                    int o,
                    Object K,
                    int bs)
Specified by:
decrypt in interface gnu.javax.crypto.cipher.IBlockCipherSpi

encrypt

public void encrypt(byte[] in,
                    int i,
                    byte[] out,
                    int o,
                    Object K,
                    int bs)
Specified by:
encrypt in interface gnu.javax.crypto.cipher.IBlockCipherSpi

isParityAdjusted

public static boolean isParityAdjusted(byte[] kb,
                                       int offset)
Test if a byte array, which must be at least 8 bytes long, is parity adjusted.
Parameters:
kb - The key bytes.
offset - The starting index into the key bytes.
Returns:
true if the first 8 bytes of kb have been parity adjusted. false otherwise.

isPossibleWeak

public static boolean isPossibleWeak(byte[] kb)
Test if the designated byte array represents a possibly weak key.
Parameters:
kb - the byte array to test.
Returns:
true if kbrepresents a possibly weak key. Returns false otherwise.

isSemiWeak

public static boolean isSemiWeak(byte[] kb)
Test if a key is a semi-weak key.
Parameters:
kb - The key to test.
Returns:
true if this key is semi-weak.

isWeak

public static boolean isWeak(byte[] kb)
Test if a key is a weak key.
Parameters:
kb - The key to test.
Returns:
true if the key is weak.

keySizes

public Iterator<E> keySizes()
Returns an Iterator over the supported key sizes. Each element returned by this object is an Integer.
Specified by:
keySizes in interface IBlockCipher
keySizes in interface gnu.javax.crypto.cipher.IBlockCipherSpi
Returns:
an Iterator over the supported key sizes.

makeKey

public Object makeKey(byte[] kb,
                      int bs)
            throws InvalidKeyException
Specified by:
makeKey in interface gnu.javax.crypto.cipher.IBlockCipherSpi
DES.java -- Copyright (C) 2002, 2003, 2006 Free Software Foundation, Inc. This file is a part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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