All Packages Class Hierarchy This Package Previous Next Index
Class cryptix.provider.elgamal.GenericElGamalParameterSet
java.lang.Object
|
+----cryptix.provider.elgamal.GenericElGamalParameterSet
- public class GenericElGamalParameterSet
- extends 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:
- 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: 1.3 $
- Author:
- David Hopwood
- See Also:
- CreateElGamalParameterSet, BaseElGamalKeyPairGenerator
-
GenericElGamalParameterSet(int[], String[][])
- Subclasses should call this constructor to determine the parameters
that will be returned by
getParameters
.
-
checkSane()
- Throws an InvalidParameterException if any of the parameters are obviously
incorrect.
-
getParameters(int)
- If primeLength corresponds to one of the precomputed prime lengths,
this method returns a corresponding ElGamalParams object.
GenericElGamalParameterSet
protected GenericElGamalParameterSet(int primeLengths[],
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: IllegalArgumentException
- if the arrays are not all the
same length.
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 InvalidParameterException
- Throws an InvalidParameterException if any of the parameters are obviously
incorrect.
All Packages Class Hierarchy This Package Previous Next Index