gnu.crypto.cipher

Class Serpent

Implemented Interfaces:
Cloneable, IBlockCipher, IBlockCipherSpi

public class Serpent
extends BaseCipher

Serpent is a 32-round substitution-permutation network block cipher, operating on 128-bit blocks and accepting keys of 128, 192, and 256 bits in length. At each round the plaintext is XORed with a 128 bit portion of the session key -- a 4224 bit key computed from the input key -- then one of eight S-boxes are applied, and finally a simple linear transformation is done. Decryption does the exact same thing in reverse order, and using the eight inverses of the S-boxes.

Serpent was designed by Ross Anderson, Eli Biham, and Lars Knudsen as a proposed cipher for the Advanced Encryption Standard.

Serpent can be sped up greatly by replacing S-box substitution with a sequence of binary operations, and the optimal implementation depends upon finding the fastest sequence of binary operations that reproduce this substitution. This implementation uses the S-boxes discovered by Dag Arne Osvik, which are optimized for the Pentium family of processors.

References:

  1. Serpent: A Candidate Block Cipher for the Advanced Encryption Standard.

Version:
$Revision: 1.8 $

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

Serpent()
Trivial zero-argument constructor.

Method Summary

Iterator
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)
Decrypts exactly one block of ciphertext.
void
encrypt(byte[] in, int i, byte[] out, int o, Object K, int bs)
Encrypts exactly one block of plaintext.
Iterator
keySizes()
Returns an Iterator over the supported key sizes.
Object
makeKey(byte[] kb, int blockSize)
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

Serpent

public Serpent()
Trivial zero-argument constructor.

Method Details

blockSizes

public Iterator 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 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)
Decrypts exactly one block of ciphertext.
Specified by:
decrypt in interface IBlockCipherSpi

Parameters:
in - the ciphertext.
out - the plaintext.
bs - the block size to use.


encrypt

public void encrypt(byte[] in,
                    int i,
                    byte[] out,
                    int o,
                    Object K,
                    int bs)
Encrypts exactly one block of plaintext.
Specified by:
encrypt in interface IBlockCipherSpi

Parameters:
in - the plaintext.
out - the ciphertext.
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 an Integer.
Specified by:
keySizes in interface IBlockCipher
keySizes in interface IBlockCipherSpi

Returns:
an Iterator over the supported key sizes.


makeKey

public Object makeKey(byte[] kb,
                      int blockSize)
            throws InvalidKeyException
Expands a user-supplied key material into a session key for a designated block size.
Specified by:
makeKey in interface IBlockCipherSpi

Parameters:

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.