gnu.crypto.assembly.Cascade Maven / Gradle / Ivy
The newest version!
package gnu.crypto.assembly;
// ----------------------------------------------------------------------------
// $Id: Cascade.java,v 1.7 2003/06/03 10:48:01 raif Exp $
//
// Copyright (C) 2003, Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 59 Temple Place - Suite 330,
// Boston, MA 02111-1307
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module. An independent module is a module which is
// not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so. If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.Set;
/**
* 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
* {@link gnu.crypto.mode.IMode}, including the {@link gnu.crypto.mode.ECB}
* mode which basically exposes a symmetric-key block cipher algorithm as a
* Mode of Operations.
*
* References:
*
*
* - [HAC]: Handbook of
* Applied Cryptography.
* CRC Press, Inc. ISBN 0-8493-8523-7, 1997
* Menezes, A., van Oorschot, P. and S. Vanstone.
*
*
* @version $Revision: 1.7 $
*/
public class Cascade {
// Constants and variables
// -------------------------------------------------------------------------
public static final String DIRECTION = "gnu.crypto.assembly.cascade.direction";
/** The map of Stages chained in this cascade. */
protected HashMap stages;
/** The ordered list of Stage UIDs to their attribute maps. */
protected LinkedList stageKeys;
/** The current operational direction of this instance. */
protected Direction wired;
/** The curently set block-size for this instance. */
protected int blockSize;
// Constructor(s)
// -------------------------------------------------------------------------
public Cascade() {
super();
stages = new HashMap(3);
stageKeys = new LinkedList();
wired = null;
blockSize = 0;
}
// Class methods
// -------------------------------------------------------------------------
/**
* Returns the Least Common Multiple of two integers.
*
* @param a the first integer.
* @param b the second integer.
* @return the LCM of abs(a) and abs(b).
*/
private static final int lcm(int a, int b) {
BigInteger A = BigInteger.valueOf(a * 1L);
BigInteger B = BigInteger.valueOf(b * 1L);
return A.multiply(B).divide(A.gcd(B)).abs().intValue();
}
// Instance methods
// -------------------------------------------------------------------------
/**
* Adds to the end of the current chain, a designated {@link Stage}.
*
* @param stage the {@link Stage} to append to the chain.
* @return a unique identifier for this stage, within this cascade.
* @throws IllegalStateException if the instance is already initialised.
* @throws IllegalArgumentException if the designated stage is already in
* the chain, or it has incompatible characteristics with the current
* elements already in the chain.
*/
public Object append(Stage stage) throws IllegalArgumentException {
return insert(size(), stage);
}
/**
* Adds to the begining of the current chain, a designated {@link Stage}.
*
* @param stage the {@link Stage} to prepend to the chain.
* @return a unique identifier for this stage, within this cascade.
* @throws IllegalStateException if the instance is already initialised.
* @throws IllegalArgumentException if the designated stage is already in
* the chain, or it has incompatible characteristics with the current
* elements already in the chain.
*/
public Object prepend(Stage stage) throws IllegalArgumentException {
return insert(0, stage);
}
/**
* Inserts a {@link Stage} into the current chain, at the specified index
* (zero-based) position.
*
* @param stage the {@link Stage} to insert into the chain.
* @return a unique identifier for this stage, within this cascade.
* @throws IllegalArgumentException if the designated stage is already in
* the chain, or it has incompatible characteristics with the current
* elements already in the chain.
* @throws IllegalStateException if the instance is already initialised.
* @throws IndexOutOfBoundsException if index is less than
* 0 or greater than the current size of this cascade.
*/
public Object insert(int index, Stage stage)
throws IllegalArgumentException, IndexOutOfBoundsException {
if (stages.containsValue(stage)) {
throw new IllegalArgumentException();
}
if (wired != null || stage == null) {
throw new IllegalStateException();
}
if (index < 0 || index > size()) {
throw new IndexOutOfBoundsException();
}
// check that there is a non-empty set of common block-sizes
Set set = stage.blockSizes();
if (stages.isEmpty()) {
if (set.isEmpty()) {
throw new IllegalArgumentException("1st stage with no block sizes");
}
} else {
Set common = this.blockSizes();
common.retainAll(set);
if (common.isEmpty()) {
throw new IllegalArgumentException("no common block sizes found");
}
}
Object result = new Object();
stageKeys.add(index, result);
stages.put(result, stage);
return result;
}
/**
* Returns the current number of stages in this chain.
*
* @return the current count of stages in this chain.
*/
public int size() {
return stages.size();
}
/**
* Returns an {@link Iterator} over the stages contained in this instance.
* Each element of this iterator is a concrete implementation of a {@link
* Stage}.
*
* @return an {@link Iterator} over the stages contained in this instance.
* Each element of the returned iterator is a concrete instance of a {@link
* Stage}.
*/
public Iterator stages() {
LinkedList result = new LinkedList();
for (Iterator it = stageKeys.listIterator(); it.hasNext(); ) {
result.addLast(stages.get(it.next()));
}
return result.listIterator();
}
/**
* Returns the {@link Set} of supported block sizes for this
* Cascade that are common to all of its chained stages. Each
* element in the returned {@link Set} is an instance of {@link Integer}.
*
* @return a {@link Set} of supported block sizes common to all the stages
* of the chain.
*/
public Set blockSizes() {
HashSet result = null;
for (Iterator it = stages.values().iterator(); it.hasNext(); ) {
Stage aStage = (Stage) it.next();
if (result == null) { // first time
result = new HashSet(aStage.blockSizes());
} else {
result.retainAll(aStage.blockSizes());
}
}
return result == null ? Collections.EMPTY_SET : result;
}
/**
* Initialises the chain for operation with specific characteristics.
*
* @param attributes a set of name-value pairs that describes the desired
* future behaviour of this instance.
* @throws IllegalStateException if the chain, or any of its stages, is
* already initialised.
* @throws InvalidKeyException if the intialisation data provided with the
* stage is incorrect or causes an invalid key to be generated.
* @see Direction#FORWARD
* @see Direction#REVERSED
*/
public void init(Map attributes) throws InvalidKeyException {
if (wired != null) {
throw new IllegalStateException();
}
Direction flow = (Direction) attributes.get(DIRECTION);
if (flow == null) {
flow = Direction.FORWARD;
}
int optimalSize = 0;
for (Iterator it = stageKeys.listIterator(); it.hasNext(); ) {
Object id = it.next();
Map attr = (Map) attributes.get(id);
attr.put(Stage.DIRECTION, flow);
Stage stage = (Stage) stages.get(id);
stage.init(attr);
optimalSize = optimalSize == 0
? stage.currentBlockSize()
: lcm(optimalSize, stage.currentBlockSize());
}
if (flow == Direction.REVERSED) { // reverse order
Collections.reverse(stageKeys);
}
wired = flow;
blockSize = optimalSize;
}
/**
* Returns the currently set block size for the chain.
*
* @return the current block size for the chain.
* @throws IllegalStateException if the instance is not initialised.
*/
public int currentBlockSize() {
if (wired == null) {
throw new IllegalStateException();
}
return blockSize;
}
/**
* Resets the chain for re-initialisation and use with other characteristics.
* This method always succeeds.
*/
public void reset() {
for (Iterator it = stageKeys.listIterator(); it.hasNext(); ) {
((Stage) stages.get(it.next())).reset();
}
if (wired == Direction.REVERSED) { // reverse it back
Collections.reverse(stageKeys);
}
wired = null;
blockSize = 0;
}
/**
* Processes exactly one block of plaintext (if initialised in the
* {@link Direction#FORWARD} state) or ciphertext (if initialised in the
* {@link Direction#REVERSED} state).
*
* @param in the plaintext.
* @param inOffset index of in from which to start considering
* data.
* @param out the ciphertext.
* @param outOffset index of out from which to store result.
* @throws IllegalStateException if the instance is not initialised.
*/
public void update(byte[] in, int inOffset, byte[] out, int outOffset) {
if (wired == null) {
throw new IllegalStateException();
}
int stageBlockSize, j, i = stages.size();
for (Iterator it = stageKeys.listIterator(); it.hasNext(); ) {
Stage stage = (Stage) stages.get(it.next());
stageBlockSize = stage.currentBlockSize();
for (j = 0; j < blockSize; j += stageBlockSize) {
stage.update(in, inOffset+j, out, outOffset+j);
}
i--;
if (i > 0) {
System.arraycopy(out, outOffset, in, inOffset, blockSize);
}
}
}
/**
* 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.
*
* @return true if the implementation passes simple
* correctness tests. Returns false otherwise.
*/
public boolean selfTest() {
for (Iterator it = stageKeys.listIterator(); it.hasNext(); ) {
if (! ((Stage) stages.get(it.next())).selfTest()) {
return false;
}
}
return true;
}
}