gnu.crypto.assembly
Class Cascade

java.lang.Object
  gnu.crypto.assembly.Cascade

public class Cascade

extends java.lang.Object

A Cascade Cipher is the concatenation of two or more block ciphers each with independent keys. Plaintext is input to the first stage; the output of stage i is input to stage i + 1; and the output of the last stage is the Cascade's ciphertext output.

In the simplest case, all stages in a Cascade have k-bit keys, and the stage inputs and outputs are all n-bit quantities. The stage ciphers may differ (general cascade of ciphers), or all be identical (cascade of identical ciphers).

The term "block ciphers" used above refers to implementations of IMode, including the ECB mode which basically exposes a symmetric-key block cipher algorithm as a Mode of Operations.

References:

1. [HAC]: Handbook of Applied Cryptography.
   CRC Press, Inc. ISBN 0-8493-8523-7, 1997
   Menezes, A., van Oorschot, P. and S. Vanstone.

Version:

$Revision: 1.2 $

Field Summary

protected int	blockSize The curently set block-size for this instance.
static java.lang.String	DIRECTION
protected java.util.LinkedList	stageKeys The ordered list of Stage UIDs to their attribute maps.
protected java.util.HashMap	stages The map of Stages chained in this cascade.
protected Direction	wired The current operational direction of this instance.

Constructor Summary

Cascade()

Method Summary

java.lang.Object	append(Stage stage) Adds to the end of the current chain, a designated Stage.
java.util.Set	blockSizes() Returns the Set of supported block sizes for this Cascade that are common to all of its chained stages.
int	currentBlockSize() Returns the currently set block size for the chain.
void	init(java.util.Map attributes) Initialises the chain for operation with specific characteristics.
java.lang.Object	insert(int index, Stage stage) Inserts a Stage into the current chain, at the specified index (zero-based) position.
java.lang.Object	prepend(Stage stage) Adds to the begining of the current chain, a designated Stage.
void	reset() Resets the chain for re-initialisation and use with other characteristics.
boolean	selfTest() Conducts a simple correctness test that consists of basic symmetric encryption / decryption test(s) for all supported block and key sizes of underlying block cipher(s) wrapped by Mode leafs.
int	size() Returns the current number of stages in this chain.
java.util.Iterator	stages() Returns an Iterator over the stages contained in this instance.
void	update(byte[] in, int inOffset, byte[] out, int outOffset) Processes exactly one block of plaintext (if initialised in the Direction.FORWARD state) or ciphertext (if initialised in the Direction.REVERSED state).

Methods inherited from class java.lang.Object

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

Field Detail

DIRECTION

public static final java.lang.String DIRECTION

See Also:

Constant Field Values

stages

protected java.util.HashMap stages

The map of Stages chained in this cascade.

stageKeys

protected java.util.LinkedList stageKeys

The ordered list of Stage UIDs to their attribute maps.

wired

protected Direction wired

The current operational direction of this instance.

blockSize

protected int blockSize

The curently set block-size for this instance.

Constructor Detail

Cascade

public Cascade()

Method Detail

append

public java.lang.Object append(Stage stage)
                        throws java.lang.IllegalArgumentException

Adds to the end of the current chain, a designated Stage.

Parameters:

stage - the Stage to append to the chain.

Returns:

a unique identifier for this stage, within this cascade.

Throws:

java.lang.IllegalStateException - if the instance is already initialised.

java.lang.IllegalArgumentException - if the designated stage is already in the chain, or it has incompatible characteristics with the current elements already in the chain.

prepend

public java.lang.Object prepend(Stage stage)
                         throws java.lang.IllegalArgumentException

Adds to the begining of the current chain, a designated Stage.

Parameters:

stage - the Stage to prepend to the chain.

Returns:

a unique identifier for this stage, within this cascade.

Throws:

java.lang.IllegalStateException - if the instance is already initialised.

java.lang.IllegalArgumentException - if the designated stage is already in the chain, or it has incompatible characteristics with the current elements already in the chain.

insert

public java.lang.Object insert(int index,
                               Stage stage)
                        throws java.lang.IllegalArgumentException,
                               java.lang.IndexOutOfBoundsException

Inserts a Stage into the current chain, at the specified index (zero-based) position.

Parameters:

stage - the Stage to insert into the chain.

Returns:

a unique identifier for this stage, within this cascade.

Throws:

java.lang.IllegalArgumentException - if the designated stage is already in the chain, or it has incompatible characteristics with the current elements already in the chain.

java.lang.IllegalStateException - if the instance is already initialised.

java.lang.IndexOutOfBoundsException - if index is less than 0 or greater than the current size of this cascade.

size

public int size()

Returns the current number of stages in this chain.

Returns:

the current count of stages in this chain.

stages

public java.util.Iterator stages()

Returns an Iterator over the stages contained in this instance. Each element of this iterator is a concrete implementation of a Stage.

Returns:

an Iterator over the stages contained in this instance. Each element of the returned iterator is a concrete instance of a Stage.

blockSizes

public java.util.Set blockSizes()

Returns the Set of supported block sizes for this Cascade that are common to all of its chained stages. Each element in the returned Set is an instance of Integer.

Returns:

a Set of supported block sizes common to all the stages of the chain.

init

public void init(java.util.Map attributes)
          throws java.security.InvalidKeyException

Initialises the chain for operation with specific characteristics.

Parameters:

attributes - a set of name-value pairs that describes the desired future behaviour of this instance.

Throws:

java.lang.IllegalStateException - if the chain, or any of its stages, is already initialised.

java.security.InvalidKeyException - if the intialisation data provided with the stage is incorrect or causes an invalid key to be generated.

See Also:

Direction.FORWARD, Direction.REVERSED

currentBlockSize

public int currentBlockSize()

Returns the currently set block size for the chain.

Returns:

the current block size for the chain.

Throws:

java.lang.IllegalStateException - if the instance is not initialised.

reset

public void reset()

Resets the chain for re-initialisation and use with other characteristics. This method always succeeds.

update

public void update(byte[] in,
                   int inOffset,
                   byte[] out,
                   int outOffset)

Processes exactly one block of plaintext (if initialised in the Direction.FORWARD state) or ciphertext (if initialised in the Direction.REVERSED state).

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 result.

Throws:

java.lang.IllegalStateException - if the instance is not initialised.

selfTest

public boolean selfTest()

Conducts a simple correctness test that consists of basic symmetric encryption / decryption test(s) for all supported block and key sizes of underlying block cipher(s) wrapped by Mode leafs. The test also includes one (1) variable key Known Answer Test (KAT) for each block cipher.

Returns:

true if the implementation passes simple correctness tests. Returns false otherwise.