gnu.crypto.cipher
Class TripleDES

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

All Implemented Interfaces:

java.lang.Cloneable, IBlockCipher, IBlockCipherSpi

public class TripleDES

extends BaseCipher

Triple-DES, 3DES, or DESede is a combined cipher that uses three iterations of the Data Encryption Standard cipher to improve the security (at the cost of speed) of plain DES.

Triple-DES runs the DES algorithm three times with three independent 56 bit keys. To encrypt:

C_i = E_k3 ( E_k2^-1 ( E_k1 ( P_i )))

And to decrypt:

P_i = E_k1^-1 ( E_k2 ( E_k3^-1 ( C_i )))

(The "ede" comes from the encryption operation, which runs Encrypt-Decrypt-Encrypt)

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. Page 294--295.

Version:

$Revision: 1.2 $

Field Summary

static int	BLOCK_SIZE Triple-DES only operates on 64 bit blocks.
static int	KEY_SIZE Triple-DES uses 168 bits of a parity-adjusted 192 bit key.

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

TripleDES()
Default 0-arguments constructor.

Method Summary

static void	adjustParity(byte[] kb, int offset) Transform a key so it will be parity adjusted.
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) Tests if a byte array has already been parity adjusted.
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

Triple-DES only operates on 64 bit blocks.

See Also:

Constant Field Values

KEY_SIZE

public static final int KEY_SIZE

Triple-DES uses 168 bits of a parity-adjusted 192 bit key.

See Also:

Constant Field Values

Constructor Detail

TripleDES

public TripleDES()

Default 0-arguments constructor.

Method Detail

adjustParity

public static void adjustParity(byte[] kb,
                                int offset)

Transform a key so it will be parity adjusted.

Parameters:

kb - The key bytes to adjust.

offset - The starting offset into the key bytes.

See Also:

DES.adjustParity(byte[],int)

isParityAdjusted

public static boolean isParityAdjusted(byte[] kb,
                                       int offset)

Tests if a byte array has already been parity adjusted.

Parameters:

kb - The key bytes to test.

offset - The starting offset into the key bytes.

Returns:

true if the bytes in kb starting at offset are parity adjusted.

See Also:

DES.isParityAdjusted(byte[],int), adjustParity(byte[],int)

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.