net.ninthtest.crypto.helix

Class HelixEncryption

java.lang.Object

net.ninthtest.crypto.helix.HelixEncryption

All Implemented Interfaces:

HelixPrimitive

public class HelixEncryption
extends Object

A Helix primitive for a single encryption operation.

Version:

1.0

Author:

Matthew Zipay (mattz@ninthtest.net)

Constructor Summary

Constructors

Constructor and Description
HelixEncryption(byte[] key, byte[] nonce) Creates a new HelixEncryption primitive using the specified key and nonce.

Method Summary

Modifier and Type	Method and Description
int	bufferSize() Returns the number of bytes that are currently buffered.
protected void	doBlock(int word) Applies a single Helix block to an input word.
byte[]	feed(byte[] part) Processes the next whole number of words (32-bit integers) from part.
byte[]	finish(byte[] part) Completes a Helix encryption/decryption operation.
byte[]	getGeneratedMac() Returns the MAC that was generated following a successful encryption/decryption operation.
protected int	nextStateWord() Returns the next state word for use in the main encryption/decryption loop.
protected int[]	transformWords(int[] plainTextWords, int mask) Performs the main encryption/decryption loop.

Methods inherited from class java.lang.Object

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

Constructor Detail

HelixEncryption

public HelixEncryption(byte[] key,
                       byte[] nonce)

Creates a new HelixEncryption primitive using the specified key and nonce.

Parameters:

key - the Helix key (cannot exceed 32 bytes in length)

nonce - the Helix nonce (must be exactly 16 bytes in length)

Method Detail

transformWords

protected int[] transformWords(int[] plainTextWords,
                               int mask)

Performs the main encryption/decryption loop.

Parameters:

plainTextWords - the next group of plaintext words to be encrypted

mask - (ignored)

Returns:

the encrypted words (ciphertext)

nextStateWord

protected final int nextStateWord()

Returns the next state word for use in the main encryption/decryption loop.

Returns:

the state word Z[0].

doBlock

protected final void doBlock(int word)

Applies a single Helix block to an input word.

Parameters:

word - a single word (32-bit integer) of plaintext or ciphertext

feed

public final byte[] feed(byte[] part)

Processes the next whole number of words (32-bit integers) from part.

Up to three bytes at the end of part may be buffered for the next call, in order to ensure that only a whole number of words are processed during this call.

Specified by:

feed in interface HelixPrimitive

Parameters:

part - the next sequence of bytes to be processed by this primitive

Returns:

an array of bytes representing plaintext or ciphertext, depending on the operation mode of this primitive

bufferSize

public final int bufferSize()

Returns the number of bytes that are currently buffered.

Specified by:

bufferSize in interface HelixPrimitive

Returns:

an integer in the range [0..3]

finish

public byte[] finish(byte[] part)

Completes a Helix encryption/decryption operation.

If this method completes successfully, the generated MAC can be retrieved using the HelixPrimitive.getGeneratedMac() method.

All remaining bytes (buffered + part) are processed. Up to three zero-bytes of padding are added to the remaining bytes to ensure that there is a whole number of words to process. Any padded bytes are masked off when the operation is completed.

If this method completes successfully, the generated MAC can be retrieved using the HelixPrimitive.getGeneratedMac() method.

Specified by:

finish in interface HelixPrimitive

Parameters:

part - the last input bytes to be fed

Returns:

the ciphertext (encryption) or plaintext (decryption) bytes

getGeneratedMac

public final byte[] getGeneratedMac()

Returns the MAC that was generated following a successful encryption/decryption operation.

Specified by:

getGeneratedMac in interface HelixPrimitive

Returns:

the generated MAC bytes

Throws:

IllegalStateException - if the encryption/decryption operation has not completed successfully