cz.d1x.dxcrypto.common

Class ConcatCombineAlgorithm

java.lang.Object

cz.d1x.dxcrypto.common.ConcatCombineAlgorithm

All Implemented Interfaces:

CombineAlgorithm

public class ConcatCombineAlgorithm
extends Object
implements CombineAlgorithm

Simplest implementation of combine algorithm. It combines inputs consecutively (simple concatenation). It implies that this algorithm needs to know length of first input if split(byte[]) will be used.

• If you expect to use only combine(byte[], byte[]), there is no need to provide the length of first input, so you can use ConcatCombineAlgorithm() constructor.
• If you expect to use both combine(byte[], byte[]) and split(byte[]), you must provide expected length of first input, so you should use ConcatCombineAlgorithm(int) constructor.

Note that this class is immutable so when this first input length is once set, then all first inputs needs to have this length, otherwise IllegalArgumentException may occur.

This algorithm is sufficient for most cases. It is not a problem for (input + salt) usage before hashing because only combine is used (split is not needed). Also it is not a problem for (IV + cipher text) during CBC because first input (IV) has always fixed length equal to cipher block size.

On the other hand, if you need split(byte[]) and expect dynamic size of both inputs, you must create new instance every time you want to combine and split.

Author:

Zdenek Obst, zdenek.obst-at-gmail.com

See Also:

SaltingAdapter, SymmetricAlgorithm

Constructor Summary

Constructors

Constructor and Description
ConcatCombineAlgorithm() Creates a new instance of combine algorithm.
ConcatCombineAlgorithm(int input1Length) Creates a new instance of combine algorithm.

Method Summary

Modifier and Type	Method and Description
byte[]	combine(byte[] input1, byte[] input2) Combines together two byte arrays.
byte[][]	split(byte[] combined) Splits input (that was combined earlier) back to original.

Methods inherited from class java.lang.Object

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

Constructor Detail

ConcatCombineAlgorithm

public ConcatCombineAlgorithm()

Creates a new instance of combine algorithm. Use this constructor if you expect use only to combine(byte[], byte[]) inputs but not split(byte[]).

ConcatCombineAlgorithm

public ConcatCombineAlgorithm(int input1Length)

Creates a new instance of combine algorithm. Use this constructor if you expect to use both combine(byte[], byte[]) and split(byte[]). You as a client are responsible to provide first input

Parameters:

input1Length - expected length of first inputs

Method Detail

combine

public byte[] combine(byte[] input1,
                      byte[] input2)

Description copied from interface: CombineAlgorithm

Combines together two byte arrays.

Specified by:

combine in interface CombineAlgorithm

Parameters:

input1 - first input to be combined

input2 - second input to be combined

Returns:

combined inputs into one

split

public byte[][] split(byte[] combined)

Description copied from interface: CombineAlgorithm

Splits input (that was combined earlier) back to original.

Specified by:

split in interface CombineAlgorithm

Parameters:

combined - previously combined input

Returns:

two dimensional array of two original inputs (byte[2][])