package gnu.crypto.key.dh;

// ----------------------------------------------------------------------------
// $Id: GnuDHKey.java,v 1.2 2005/10/06 04:24:16 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING.  If not, write to the
//
//    Free Software Foundation Inc.,
//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module.  An independent module is a module which is
// not derived from or based on this library.  If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so.  If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;

import java.math.BigInteger;
import java.security.Key;

import javax.crypto.interfaces.DHKey;
import javax.crypto.spec.DHParameterSpec;

/**
 * <p>A base asbtract class for both public and private Diffie-Hellman keys. It
 * encapsulates the two DH numbers: <code>p</code>, and <code>g</code>.</p>
 *
 * <p>According to the JDK, cryptographic <i>Keys</i> all have a <i>format</i>.
 * The format used in this implementation is called <i>Raw</i>, and basically
 * consists of the raw byte sequences of algorithm parameters. The exact order
 * of the byte sequences and the implementation details are given in each of
 * the relevant <code>getEncoded()</code> methods of each of the private and
 * public keys.</p>
 *
 * <p>Reference:</p>
 * <ol>
 *    <li><a href="http://www.ietf.org/rfc/rfc2631.txt">Diffie-Hellman Key
 *    Agreement Method</a><br>
 *    Eric Rescorla.</li>
 * </ol>
 *
 * @version $Revision: 1.2 $
 */
public abstract class GnuDHKey implements Key, DHKey {

   // Constants and variables
   // -------------------------------------------------------------------------

   /** The public prime q. A prime divisor of p-1. */
   protected BigInteger q;

   /** The public prime p. */
   protected BigInteger p;

   /** The generator g. */
   protected BigInteger g;

   // Constructor(s)
   // -------------------------------------------------------------------------

   /**
    * <p>Trivial protected constructor.</p>
    *
    * @param q a prime divisor of p-1.
    * @param p the public prime.
    * @param g the generator of the group.
    */
   protected GnuDHKey(BigInteger q, BigInteger p, BigInteger g) {
      super();

      this.q = q;
      this.p = p;
      this.g = g;
   }

   // Class methods
   // -------------------------------------------------------------------------

   // Instance methods
   // -------------------------------------------------------------------------

   // javax.crypto.interfaces.DHKey interface implementation ------------------

   public DHParameterSpec getParams() {
      if (q == null) {
         return new DHParameterSpec(p, g);
      } else {
         return new DHParameterSpec(p, g, q.bitLength());
      }
   }

   // java.security.Key interface implementation ------------------------------

   public String getAlgorithm() {
      return Registry.DH_KPG;
   }

   public String getFormat() {
      return null;
   }

   // Other instance methods --------------------------------------------------

   public BigInteger getQ() {
      return q;
   }

   /**
    * <p>Returns <code>true</code> if the designated object is an instance of
    * {@link DHKey} and has the same Diffie-Hellman parameter values as this
    * one.</p>
    *
    * @param obj the other non-null DH key to compare to.
    * @return <code>true</code> if the designated object is of the same type and
    * value as this one.
    */
   public boolean equals(Object obj) {
      if (obj == null) {
         return false;
      }
      if (!(obj instanceof DHKey)) {
         return false;
      }
      DHKey that = (DHKey) obj;
      return p.equals(that.getParams().getP()) && g.equals(that.getParams().getG());
   }
}
