cz.d1x.dxcrypto.common

Class ConcatAlgorithm

java.lang.Object

cz.d1x.dxcrypto.common.ConcatAlgorithm

All Implemented Interfaces:

CombineAlgorithm, CombineSplitAlgorithm, SplitAlgorithm

public class ConcatAlgorithm
extends Object
implements CombineSplitAlgorithm

Simplest implementation of combine/split 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 ConcatAlgorithm() 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 ConcatAlgorithm(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 has usage for input and salt combination before hashing because only combine operation is used (split is not needed). It can be also used for IV and cipher text combine/split 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, SymmetricCryptoAlgorithm

Constructor Summary

Constructors

Constructor and Description
ConcatAlgorithm() Creates a new instance of combine algorithm.
ConcatAlgorithm(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

ConcatAlgorithm

public ConcatAlgorithm()

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

ConcatAlgorithm

public ConcatAlgorithm(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: SplitAlgorithm

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

Specified by:

split in interface SplitAlgorithm

Parameters:

combined - previously combined input

Returns:

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