org.bouncycastle.crypto.engines
Class ElGamalEngine

java.lang.Object
  org.bouncycastle.crypto.engines.ElGamalEngine

All Implemented Interfaces:

AsymmetricBlockCipher

public class ElGamalEngine
extends java.lang.Object
implements AsymmetricBlockCipher

this does your basic ElGamal algorithm.

Field Summary

private int	bitSize
private boolean	forEncryption
private ElGamalKeyParameters	key
private static java.math.BigInteger	ONE
private java.security.SecureRandom	random
private static java.math.BigInteger	TWO
private static java.math.BigInteger	ZERO

Constructor Summary

ElGamalEngine()

Method Summary

int	getInputBlockSize() Return the maximum size for an input block to this engine.
int	getOutputBlockSize() Return the maximum size for an output block to this engine.
void	init(boolean forEncryption, CipherParameters param) initialise the ElGamal engine.
byte[]	processBlock(byte[] in, int inOff, int inLen) Process a single block using the basic ElGamal algorithm.

Methods inherited from class java.lang.Object

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

Field Detail

key

private ElGamalKeyParameters key

random

private java.security.SecureRandom random

forEncryption

private boolean forEncryption

bitSize

private int bitSize

ZERO

private static final java.math.BigInteger ZERO

ONE

private static final java.math.BigInteger ONE

TWO

private static final java.math.BigInteger TWO

Constructor Detail

ElGamalEngine

public ElGamalEngine()

Method Detail

init

public void init(boolean forEncryption,
                 CipherParameters param)

initialise the ElGamal engine.

Specified by:

init in interface AsymmetricBlockCipher

Parameters:

forEncryption - true if we are encrypting, false otherwise.

param - the necessary ElGamal key parameters.

getInputBlockSize

public int getInputBlockSize()

Return the maximum size for an input block to this engine. For ElGamal this is always one byte less than the size of P on encryption, and twice the length as the size of P on decryption.

Specified by:

getInputBlockSize in interface AsymmetricBlockCipher

Returns:

maximum size for an input block.

getOutputBlockSize

public int getOutputBlockSize()

Return the maximum size for an output block to this engine. For ElGamal this is always one byte less than the size of P on decryption, and twice the length as the size of P on encryption.

Specified by:

getOutputBlockSize in interface AsymmetricBlockCipher

Returns:

maximum size for an output block.

processBlock

public byte[] processBlock(byte[] in,
                           int inOff,
                           int inLen)

Process a single block using the basic ElGamal algorithm.

Specified by:

processBlock in interface AsymmetricBlockCipher

Parameters:

in - the input array.

inOff - the offset into the input buffer where the data starts.

inLen - the length of the data to be processed.

Returns:

the result of the ElGamal process.

Throws:

DataLengthException - the input block is too large.