gnu.crypto.cipher

Class Twofish

Implemented Interfaces:
Cloneable, IBlockCipher, IBlockCipherSpi

public final class Twofish
extends BaseCipher

Twofish is a balanced 128-bit Feistel cipher, consisting of 16 rounds. In each round, a 64-bit S-box value is computed from 64 bits of the block, and this value is xored into the other half of the block. The two half-blocks are then exchanged, and the next round begins. Before the first round, all input bits are xored with key-dependent "whitening" subkeys, and after the final round the output bits are xored with other key-dependent whitening subkeys; these subkeys are not used anywhere else in the algorithm.

Twofish is designed by Bruce Schneier, Doug Whiting, John Kelsey, Chris Hall, David Wagner and Niels Ferguson.

References:

  1. Twofish: A 128-bit Block Cipher.
Version:
$Revision: 1.10 $

Field Summary

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

Twofish()
Trivial 0-arguments constructor.

Method Summary

Iterator
blockSizes()
Returns an Iterator over the supported block sizes.
Object
clone()
void
decrypt(byte[] in, int inOffset, byte[] out, int outOffset, Object sessionKey, int bs)
Decrypts exactly one block of ciphertext.
void
encrypt(byte[] in, int inOffset, byte[] out, int outOffset, Object sessionKey, int bs)
Encrypts exactly one block of plaintext.
Iterator
keySizes()
Returns an Iterator over the supported key sizes.
Object
makeKey(byte[] k, int bs)
Expands a user-supplied key material into a session key for a designated block size.
boolean
selfTest()
A correctness test that consists of basic symmetric encryption / decryption test(s) for all supported block and key sizes, as well as one (1) variable key Known Answer Test (KAT).

Methods inherited from class gnu.crypto.cipher.BaseCipher

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

Constructor Details

Twofish

public Twofish()
Trivial 0-arguments constructor.

Method Details

blockSizes

public Iterator blockSizes()
Returns an Iterator over the supported block sizes. Each element returned by this object is a Integer.
Specified by:
blockSizes in interface IBlockCipher
blockSizes in interface IBlockCipherSpi
Returns:
an Iterator over the supported block sizes.

clone

public Object clone()
Specified by:
clone in interface IBlockCipher
Overrides:
clone in interface BaseCipher

decrypt

public void decrypt(byte[] in,
                    int inOffset,
                    byte[] out,
                    int outOffset,
                    Object sessionKey,
                    int bs)
Decrypts exactly one block of ciphertext.
Specified by:
decrypt in interface IBlockCipherSpi
Parameters:
in - the ciphertext.
inOffset - index of in from which to start considering data.
out - the plaintext.
outOffset - index of out from which to store the result.
bs - the block size to use.

encrypt

public void encrypt(byte[] in,
                    int inOffset,
                    byte[] out,
                    int outOffset,
                    Object sessionKey,
                    int bs)
Encrypts exactly one block of plaintext.
Specified by:
encrypt in interface IBlockCipherSpi
Parameters:
in - the plaintext.
inOffset - index of in from which to start considering data.
out - the ciphertext.
outOffset - index of out from which to store the result.
bs - the block size to use.

keySizes

public Iterator keySizes()
Returns an Iterator over the supported key sizes. Each element returned by this object is a Integer.
Specified by:
keySizes in interface IBlockCipher
keySizes in interface IBlockCipherSpi
Returns:
an Iterator over the supported key sizes.

makeKey

public Object makeKey(byte[] k,
                      int bs)
            throws InvalidKeyException
Expands a user-supplied key material into a session key for a designated block size.
Specified by:
makeKey in interface IBlockCipherSpi
Parameters:
k - the 64/128/192/256-bit user-key to use.
bs - the desired block size in bytes.
Returns:
an Object encapsulating the session key.

selfTest

public boolean selfTest()
A correctness test that consists of basic symmetric encryption / decryption test(s) for all supported block and key sizes, as well as one (1) variable key Known Answer Test (KAT).
Specified by:
selfTest in interface IBlockCipher
selfTest in interface IBlockCipherSpi
Overrides:
selfTest in interface BaseCipher
Returns:
true if the implementation passes simple correctness tests. Returns false otherwise.

Copyright © 2001, 2002, 2003 Free Software Foundation, Inc. All Rights Reserved.