gnu.crypto.cipher

Class DES

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.

Version: $Revision: 1.4 $

Nested Class Summary
classDES.Context
Simple wrapper class around the session keys.
Field Summary
static intBLOCK_SIZE
DES operates on 64 bit blocks.
static intKEY_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.
Constructor Summary
DES()
Default 0-argument constructor.
Method Summary
static voidadjustParity(byte[] kb, int offset)

Adjust the parity for a raw key array.

IteratorblockSizes()
Objectclone()
voiddecrypt(byte[] in, int i, byte[] out, int o, Object K, int bs)
voidencrypt(byte[] in, int i, byte[] out, int o, Object K, int bs)
static booleanisParityAdjusted(byte[] kb, int offset)

Test if a byte array, which must be at least 8 bytes long, is parity adjusted.

static booleanisPossibleWeak(byte[] kb)

Test if the designated byte array represents a possibly weak key.

static booleanisSemiWeak(byte[] kb)

Test if a key is a semi-weak key.

static booleanisWeak(byte[] kb)

Test if a key is a weak key.

IteratorkeySizes()
ObjectmakeKey(byte[] kb, int bs)

Field Detail

BLOCK_SIZE

public static final int BLOCK_SIZE
DES operates on 64 bit blocks.

KEY_SIZE

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

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 Detail

DES

public DES()
Default 0-argument constructor.

Method Detail

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 blockSizes()

clone

public Object clone()

decrypt

public void decrypt(byte[] in, int i, byte[] out, int o, Object K, int bs)

encrypt

public void encrypt(byte[] in, int i, byte[] out, int o, Object K, int bs)

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 keySizes()

makeKey

public Object makeKey(byte[] kb, int bs)
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