iaik.security.dh

Class ESDHParameterGenerator

java.lang.Object

java.security.AlgorithmParameterGeneratorSpi

iaik.security.dh.DHParameterGenerator

iaik.security.dh.ESDHParameterGenerator

public class ESDHParameterGenerator
extends DHParameterGenerator

This class implements an AlgorithmParameterGenerator that generates parameters for key-agreement according to the Diffie-Hellman protocol.

The algorithm used is taken from RFC 2631. It specifies a minimum prime length of 512 bit and minimum exponent length of 160 bit; defaults in this implementation are 1024 and 300 bits respectively. Access to the verification parameters provided by the generation algorithm is not possible with the current API.

Note that parameter generation is fairly slow but this should not be a problem as this is a hardly performed activity anyway. Typically they will be generated once per user group by the CA and then the users will generate their keys using the parameters provided.

The Diffie Hellman algorithm has been the first public-key algorithm. It only can be used for key-agreement, but not for data encrypting and decrypting.

PKCS#3 describes a method for implementing the Diffie Hellman key agreement where two (or more) entities use general Diffie Hellman parameters (an odd prime p, an integer base g satisfying 0 < g < p, and optionally an integer l prescribing the length of the private value), generated from some central authority (which may an entity itself), for creating a shared secret only known by them.

Applications shall use AlgorithmParameterGenerator.getInstance("ESDH") for obtaining an AlgorithmParamterGenerator for generating ESDH parameters in opaque representation. Once the generator has been created, it shall be properly initialized by one of the several init methods. If none explicit initialization is done, per default the length of the prime modulus is set to 512 bits and the length of the exponent (private value) is chosen to be 8 bits shorter, i.e. 504 bits. After initializing the generator (or relying on default settings), the reguired parameters actually are created by calling the generateParameters method.

See Also:

AlgorithmParameterGenerator, javax.crypto.spec.ESDHParameterSpec, ESDHParameters, ESDHPublicKey, ESDHPrivateKey, ESDHKeyPairGenerator, ESDHKeyFactory, ESDHKeyAgreement

Constructor Summary

Constructors

Constructor and Description
ESDHParameterGenerator() The default constructor.

Method Summary

Methods

Modifier and Type	Method and Description
protected java.security.AlgorithmParameters	createAlgParams(java.math.BigInteger p, java.math.BigInteger g, java.math.BigInteger q, java.math.BigInteger j, byte[] seed, int counter) Actually generates the required DH AlgorithmParameters.

Methods inherited from class iaik.security.dh.DHParameterGenerator

engineGenerateParameters, engineInit, engineInit

Methods inherited from class java.lang.Object

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

Constructor Detail

ESDHParameterGenerator

public ESDHParameterGenerator()

The default constructor. Only internally used for creating an ESDHParameterGenerator object. Applications shall use one of the AlgorithmParameterGenerator.getInstance factory methods for obtaining an AlgorithmParamterGenerator for generating paramters for Diffie Hellman key agreement.

Method Detail

createAlgParams

protected java.security.AlgorithmParameters createAlgParams(java.math.BigInteger p,
                                                java.math.BigInteger g,
                                                java.math.BigInteger q,
                                                java.math.BigInteger j,
                                                byte[] seed,
                                                int counter)

Actually generates the required DH AlgorithmParameters.

Applications shall call generatePrameters() for provider independently accessing this method.

Returns:

the new created Diffie Hellman AlgorithmParameters