AlgIdDSA

Class Overview

This class identifies DSS/DSA Algorithm variants, which are distinguished by using different algorithm parameters P, Q, G. It uses the NIST/IETF standard DER encoding. These are used to implement the Digital Signature Standard (DSS), FIPS 186.

NOTE: DSS/DSA Algorithm IDs may be created without these parameters. Use of DSS/DSA in modes where parameters are either implicit (e.g. a default applicable to a site or a larger scope), or are derived from some Certificate Authority's DSS certificate, is not supported directly. The application is responsible for creating a key containing the required parameters prior to using the key in cryptographic operations. The follwoing is an example of how this may be done assuming that we have a certificate called currentCert which doesn't contain DSS/DSA parameters and we need to derive DSS/DSA parameters from a CA's certificate called caCert.

 // key containing parameters to use
 DSAPublicKey cAKey = (DSAPublicKey)(caCert.getPublicKey());
 // key without parameters
 DSAPublicKey nullParamsKey = (DSAPublicKey)(currentCert.getPublicKey());

 DSAParams cAKeyParams = cAKey.getParams();
 KeyFactory kf = KeyFactory.getInstance("DSA");
 DSAPublicKeySpec ks = new DSAPublicKeySpec(nullParamsKey.getY(),
                                            cAKeyParams.getP(),
                                            cAKeyParams.getQ(),
                                            cAKeyParams.getG());
 DSAPublicKey usableKey = kf.generatePublic(ks);