net.java.truevfs.comp.zip.crypto

Class CtrBlockCipher

java.lang.Object

net.java.truevfs.comp.zip.crypto.CtrBlockCipher

All Implemented Interfaces:

SeekableBlockCipher, BlockCipher

public class CtrBlockCipher
extends Object
implements SeekableBlockCipher

Implements Counter (CTR) mode (alias Segmented Integer Counter - SIC) on top of a simple block cipher. This code is based on bouncy castle's SICBlockCipher class, but allows random access to a block, too. Like the SICBlockCipher class, the block counter is incremented after updating the cipher input in big endian order.

Author:

The Legion of the Bouncy Castle (majority of the code), Christian Schlichtherle (optimizations and extension to support seeking)

Field Summary

Fields

Modifier and Type	Field and Description
protected long	blockCounter
protected int	blockSize
protected BlockCipher	cipher
protected byte[]	cipherIn
protected byte[]	cipherOut
protected byte[]	IV

Constructor Summary

Constructors

Constructor and Description
CtrBlockCipher(BlockCipher cipher) Constructs a new CTR block cipher.

Method Summary

Modifier and Type	Method and Description
String	getAlgorithmName()
long	getBlockCounter() Returns the index of the block, starting at 0, which will be processed next when BlockCipher.processBlock(byte[], int, byte[], int) is called.
int	getBlockSize()
protected void	incCounter()
void	init(boolean forEncryption, CipherParameters params)
int	processBlock(byte[] in, int inOff, byte[] out, int outOff)
void	reset()
void	setBlockCounter(long blockCounter) Sets the counter so that the block with the given index, starting at 0, can be processed next.

Methods inherited from class java.lang.Object

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

Field Detail

blockCounter

protected long blockCounter

blockSize

protected final int blockSize

cipher

protected final BlockCipher cipher

cipherIn

protected final byte[] cipherIn

cipherOut

protected final byte[] cipherOut

IV

protected final byte[] IV

Constructor Detail

CtrBlockCipher

public CtrBlockCipher(BlockCipher cipher)

Constructs a new CTR block cipher.

Parameters:

cipher - The underlying block cipher to use.

Method Detail

getAlgorithmName

public String getAlgorithmName()

Specified by:

getAlgorithmName in interface BlockCipher

getBlockCounter

public long getBlockCounter()

Description copied from interface: SeekableBlockCipher

Returns the index of the block, starting at 0, which will be processed next when BlockCipher.processBlock(byte[], int, byte[], int) is called.

Specified by:

getBlockCounter in interface SeekableBlockCipher

getBlockSize

public int getBlockSize()

Specified by:

getBlockSize in interface BlockCipher

incCounter

protected void incCounter()

init

public void init(boolean forEncryption,
                 CipherParameters params)

Specified by:

init in interface BlockCipher

processBlock

public final int processBlock(byte[] in,
                              int inOff,
                              byte[] out,
                              int outOff)
                       throws DataLengthException,
                              IllegalStateException

Specified by:

processBlock in interface BlockCipher

Throws:

DataLengthException

IllegalStateException

reset

public void reset()

Specified by:

reset in interface BlockCipher

setBlockCounter

public void setBlockCounter(long blockCounter)

Description copied from interface: SeekableBlockCipher

Sets the counter so that the block with the given index, starting at 0, can be processed next.

Specified by:

setBlockCounter in interface SeekableBlockCipher

Parameters:

blockCounter - The index of the block, starting at 0, which will be processed next when BlockCipher.processBlock(byte[], int, byte[], int) is called.