gnu.crypto.cipher
Class DES

java.lang.Object
  gnu.crypto.cipher.BaseCipher
      gnu.crypto.cipher.DES

All Implemented Interfaces:

java.lang.Cloneable, IBlockCipher, 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.

Version:

$Revision: 1.2 $

Nested Class Summary

(package private) class

DES.Context Simple wrapper class around the session keys.

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.crypto.cipher.BaseCipher

currentBlockSize, currentKey, defaultBlockSize, defaultKeySize, lock, name

Fields inherited from interface gnu.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.
java.util.Iterator	blockSizes() Returns an Iterator over the supported block sizes.
java.lang.Object	clone() Returns a clone of this instance.
void	decrypt(byte[] in, int i, byte[] out, int o, java.lang.Object K, int bs) Decrypts exactly one block of ciphertext.
void	encrypt(byte[] in, int i, byte[] out, int o, java.lang.Object K, int bs) Encrypts exactly one block of plaintext.
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.
java.util.Iterator	keySizes() Returns an Iterator over the supported key sizes.
java.lang.Object	makeKey(byte[] kb, int bs) Expands a user-supplied key material into a session key for a designated block size.

Methods inherited from class gnu.crypto.cipher.BaseCipher

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

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BLOCK_SIZE

public static final int BLOCK_SIZE

DES operates on 64 bit blocks.

See Also:

Constant Field Values

KEY_SIZE

public static final int KEY_SIZE

DES uses 56 bits of a 64 bit parity-adjusted key.

See Also:

Constant Field Values

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.

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.

POSSIBLE_WEAK_KEYS

public static final byte[][] POSSIBLE_WEAK_KEYS

Possible weak keys (parity adjusted) --produce 4 instead of 16 subkeys.

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.

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.

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.

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.

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.

clone

public java.lang.Object clone()

Description copied from interface: IBlockCipher

Returns a clone of this instance.

Specified by:

clone in interface IBlockCipher

Specified by:

clone in class BaseCipher

blockSizes

public java.util.Iterator blockSizes()

Description copied from interface: IBlockCipher

Returns an Iterator over the supported block sizes. Each element returned by this object is an Integer.

Returns:

an Iterator over the supported block sizes.

keySizes

public java.util.Iterator keySizes()

Description copied from interface: IBlockCipher

Returns an Iterator over the supported key sizes. Each element returned by this object is an Integer.

Returns:

an Iterator over the supported key sizes.

makeKey

public java.lang.Object makeKey(byte[] kb,
                                int bs)
                         throws java.security.InvalidKeyException

Description copied from interface: IBlockCipherSpi

Expands a user-supplied key material into a session key for a designated block size.

Parameters:

kb - the user-supplied key material.

bs - the desired block size in bytes.

Returns:

an Object encapsulating the session key.

Throws:

java.security.InvalidKeyException - if the key data is invalid.

encrypt

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

Description copied from interface: IBlockCipherSpi

Encrypts exactly one block of plaintext.

Parameters:

in - the plaintext.

i - index of in from which to start considering data.

out - the ciphertext.

o - index of out from which to store the result.

K - the session key to use.

bs - the block size to use.

decrypt

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

Description copied from interface: IBlockCipherSpi

Decrypts exactly one block of ciphertext.

Parameters:

in - the ciphertext.

i - index of in from which to start considering data.

out - the plaintext.

o - index of out from which to store the result.

K - the session key to use.

bs - the block size to use.