Class Twofish

java.lang.Object
  Twofish

public final class Twofish

extends Object

Twofish is an AES candidate algorithm. It 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 was submitted by Bruce Schneier, Doug Whiting, John Kelsey, Chris Hall and David Wagner.

Reference:

1. TWOFISH2.C -- Optimized C API calls for TWOFISH AES submission, Version 1.00, April 1998, by Doug Whiting.

Copyright © 1998 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: #3 $

Author:

Raif S. Naffah

Field Summary

(package private) static int	BLOCK_SIZE
private static int	GF256_FDBK Primitive polynomial for GF(256)
private static int	GF256_FDBK_2
private static int	GF256_FDBK_4
private static char[]	HEX_DIGITS data for hexadecimal visualisation.
private static int	INPUT_WHITEN
private static int	MAX_ROUNDS
private static int[][]	MDS MDS matrix
private static int	OUTPUT_WHITEN
private static byte[][]	P Fixed 8x8 permutation S-boxes
private static int	P_00 Define the fixed p0/p1 permutations used in keyed S-box lookup.
private static int	P_01
private static int	P_02
private static int	P_03
private static int	P_04
private static int	P_10
private static int	P_11
private static int	P_12
private static int	P_13
private static int	P_14
private static int	P_20
private static int	P_21
private static int	P_22
private static int	P_23
private static int	P_24
private static int	P_30
private static int	P_31
private static int	P_32
private static int	P_33
private static int	P_34
private static int	ROUND_SUBKEYS
private static int	ROUNDS
private static int	RS_GF_FDBK
private static int	SK_BUMP
private static int	SK_ROTL
private static int	SK_STEP
private static int	TOTAL_SUBKEYS

Constructor Summary

Twofish()

Method Summary

private static int	_b(int x, int N)
private static boolean	areEqual(byte[] a, byte[] b)
private static int	b0(int x)
private static int	b1(int x)
private static int	b2(int x)
private static int	b3(int x)
static byte[]	blockDecrypt(byte[] in, int inOffset, Object sessionKey) Decrypt exactly one block of ciphertext.
static byte[]	blockEncrypt(byte[] in, int inOffset, Object sessionKey) Encrypt exactly one block of plaintext.
static int	blockSize()
private static int	F32(int k64Cnt, int x, int[] k32)
private static int	Fe32(int[] sBox, int x, int R)
private static String	intToString(int n) Returns a string of 8 hexadecimal digits (most significant digit first) corresponding to the integer n, which is treated as unsigned.
private static int	LFSR1(int x)
private static int	LFSR2(int x)
static Object	makeKey(byte[] k) Expand a user-supplied key material into a session key.
private static int	Mx_1(int x)
private static int	Mx_X(int x)
private static int	Mx_Y(int x)
private static int	RS_MDS_Encode(int k0, int k1) Use (12, 8) Reed-Solomon code over GF(256) to produce a key S-box 32-bit entity from two key material 32-bit entities.
private static int	RS_rem(int x)
static boolean	self_test() A basic symmetric encryption/decryption test.
private static boolean	self_test(int keysize) A basic symmetric encryption/decryption test for a given key size.
private static String	toString(byte[] ba) Returns a string of hexadecimal digits from a byte array.
private static String	toString(byte[] ba, int offset, int length)

Methods inherited from class java.lang.Object

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

Field Detail

BLOCK_SIZE

static final int BLOCK_SIZE

See Also:

Constant Field Values

ROUNDS

private static final int ROUNDS

See Also:

Constant Field Values

MAX_ROUNDS

private static final int MAX_ROUNDS

See Also:

Constant Field Values

INPUT_WHITEN

private static final int INPUT_WHITEN

See Also:

Constant Field Values

OUTPUT_WHITEN

private static final int OUTPUT_WHITEN

See Also:

Constant Field Values

ROUND_SUBKEYS

private static final int ROUND_SUBKEYS

See Also:

Constant Field Values

TOTAL_SUBKEYS

private static final int TOTAL_SUBKEYS

See Also:

Constant Field Values

SK_STEP

private static final int SK_STEP

See Also:

Constant Field Values

SK_BUMP

private static final int SK_BUMP

See Also:

Constant Field Values

SK_ROTL

private static final int SK_ROTL

See Also:

Constant Field Values

P

private static final byte[][] P

Fixed 8x8 permutation S-boxes

P_00

private static final int P_00

Define the fixed p0/p1 permutations used in keyed S-box lookup. By changing the following constant definitions, the S-boxes will automatically get changed in the Twofish engine.

See Also:

Constant Field Values

P_01

private static final int P_01

See Also:

Constant Field Values

P_02

private static final int P_02

See Also:

Constant Field Values

P_03

private static final int P_03

See Also:

Constant Field Values

P_04

private static final int P_04

See Also:

Constant Field Values

P_10

private static final int P_10

See Also:

Constant Field Values

P_11

private static final int P_11

See Also:

Constant Field Values

P_12

private static final int P_12

See Also:

Constant Field Values

P_13

private static final int P_13

See Also:

Constant Field Values

P_14

private static final int P_14

See Also:

Constant Field Values

P_20

private static final int P_20

See Also:

Constant Field Values

P_21

private static final int P_21

See Also:

Constant Field Values

P_22

private static final int P_22

See Also:

Constant Field Values

P_23

private static final int P_23

See Also:

Constant Field Values

P_24

private static final int P_24

See Also:

Constant Field Values

P_30

private static final int P_30

See Also:

Constant Field Values

P_31

private static final int P_31

See Also:

Constant Field Values

P_32

private static final int P_32

See Also:

Constant Field Values

P_33

private static final int P_33

See Also:

Constant Field Values

P_34

private static final int P_34

See Also:

Constant Field Values

GF256_FDBK

private static final int GF256_FDBK

Primitive polynomial for GF(256)

See Also:

Constant Field Values

GF256_FDBK_2

private static final int GF256_FDBK_2

See Also:

Constant Field Values

GF256_FDBK_4

private static final int GF256_FDBK_4

See Also:

Constant Field Values

MDS

private static final int[][] MDS

MDS matrix

RS_GF_FDBK

private static final int RS_GF_FDBK

See Also:

Constant Field Values

HEX_DIGITS

private static final char[] HEX_DIGITS

data for hexadecimal visualisation.

Constructor Detail

Twofish

public Twofish()

Method Detail

LFSR1

private static final int LFSR1(int x)

LFSR2

private static final int LFSR2(int x)

Mx_1

private static final int Mx_1(int x)

Mx_X

private static final int Mx_X(int x)

Mx_Y

private static final int Mx_Y(int x)

makeKey

public static Object makeKey(byte[] k)
                      throws InvalidKeyException

Expand a user-supplied key material into a session key.

Parameters:

k - The 64/128/192/256-bit user-key to use.

Returns:

This cipher's round keys.

Throws:

InvalidKeyException - If the key is invalid.

blockEncrypt

public static byte[] blockEncrypt(byte[] in,
                                  int inOffset,
                                  Object sessionKey)

Encrypt exactly one block of plaintext.

Parameters:

in - The plaintext.

inOffset - Index of in from which to start considering data.

sessionKey - The session key to use for encryption.

Returns:

The ciphertext generated from a plaintext using the session key.

blockDecrypt

public static byte[] blockDecrypt(byte[] in,
                                  int inOffset,
                                  Object sessionKey)

Decrypt exactly one block of ciphertext.

Parameters:

in - The ciphertext.

inOffset - Index of in from which to start considering data.

sessionKey - The session key to use for decryption.

Returns:

The plaintext generated from a ciphertext using the session key.

self_test

public static boolean self_test()

A basic symmetric encryption/decryption test.

b0

private static final int b0(int x)

b1

private static final int b1(int x)

b2

private static final int b2(int x)

b3

private static final int b3(int x)

RS_MDS_Encode

private static final int RS_MDS_Encode(int k0,
                                       int k1)

Use (12, 8) Reed-Solomon code over GF(256) to produce a key S-box 32-bit entity from two key material 32-bit entities.

Parameters:

k0 - 1st 32-bit entity.

k1 - 2nd 32-bit entity.

Returns:

Remainder polynomial generated using RS code

RS_rem

private static final int RS_rem(int x)

F32

private static final int F32(int k64Cnt,
                             int x,
                             int[] k32)

Fe32

private static final int Fe32(int[] sBox,
                              int x,
                              int R)

_b

private static final int _b(int x,
                            int N)

blockSize

public static int blockSize()

Returns:

The length in bytes of the Algorithm input block.

self_test

private static boolean self_test(int keysize)

A basic symmetric encryption/decryption test for a given key size.

areEqual

private static boolean areEqual(byte[] a,
                                byte[] b)

Returns:

True iff the arrays have identical contents.

intToString

private static String intToString(int n)

Returns a string of 8 hexadecimal digits (most significant digit first) corresponding to the integer n, which is treated as unsigned.

toString

private static String toString(byte[] ba)

Returns a string of hexadecimal digits from a byte array. Each byte is converted to 2 hex symbols.

toString

private static String toString(byte[] ba,
                               int offset,
                               int length)