cryptix.provider.elgamal

Class GenericElGamalParameterSet

java.lang.Object

cryptix.provider.elgamal.GenericElGamalParameterSet

Direct Known Subclasses:

DefaultElGamalParameterSet

public class GenericElGamalParameterSet
extends java.lang.Object

This class represents a set of ElGamal parameters for various prime lengths.

The best methods for computing discrete logarithms in GF(p) have an expensive pre-computation stage, but once the pre-computation has been done, individual logarithms can be calculated quickly. In order to make sure that a particular set of parameters does not become too much of a target because it is used in more than one application, you may wish to generate your own set of parameters.

References:

1. Bruce Schneier, "Section 11.3 Number Theory" (heading "Calculating Discrete Logarithms in a Finite Group," pages 262-263), Applied Cryptography, 2nd edition, John Wiley & Sons, 1996.

Copyright © 1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.4 $

Since:

Cryptix 2.2.2

Author:

David Hopwood

See Also:

cryptix.examples.CreateElGamalParameterSet, cryptix.security.elgamal.BaseElGamalKeyPairGenerator

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	GenericElGamalParameterSet(int[] primeLengths, java.lang.String[][] precomputed) Subclasses should call this constructor to determine the parameters that will be returned by getParameters.

Method Summary

Modifier and Type	Method and Description
void	checkSane() Throws an InvalidParameterException if any of the parameters are obviously incorrect.
ElGamalParams	getParameters(int primeLength) If primeLength corresponds to one of the precomputed prime lengths, this method returns a corresponding ElGamalParams object.

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericElGamalParameterSet

protected GenericElGamalParameterSet(int[] primeLengths,
                                     java.lang.String[][] precomputed)

Subclasses should call this constructor to determine the parameters that will be returned by getParameters.

Parameters:

primeLengths - an array of bit lengths for each prime

precomputedP - an array of hex strings representing each prime

precomputedG - an array of hex strings representing each base

Throws:

java.lang.IllegalArgumentException - if the arrays are not all the same length.

Method Detail

getParameters

public ElGamalParams getParameters(int primeLength)

If primeLength corresponds to one of the precomputed prime lengths, this method returns a corresponding ElGamalParams object. Otherwise, it returns null.

checkSane

public void checkSane()
               throws java.security.InvalidParameterException

Throws an InvalidParameterException if any of the parameters are obviously incorrect.

Throws:

java.security.InvalidParameterException