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/* SRPKey.java --

   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath 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 of the License, or (at

your option) any later version.

GNU Classpath 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 GNU Classpath; if not, write to the Free Software

Foundation, Inc., 51 Franklin St, 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.  */

package gnu.javax.crypto.key.srp6;

import gnu.java.security.Registry;

import gnu.java.security.key.IKeyPairCodec;

import java.io.Serializable;

import java.math.BigInteger;

import java.security.Key;

/**

 * An abstract representation of a base SRP ephemeral key.

 * <p>

 * This object encapsulates the two numbers:

 * <ul>

 * <li><b>N</b>: A large safe prime (N = 2q+1, where q is prime).</li>

 * <li><b>g</b>: A generator modulo N.</li>

 * </ul>

 * <p>

 * Note that in SRP, all arithmetic is done modulo N.

 * <p>

 * Reference:

 * <ol>

 * <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br>

 * Thomas J. Wu.</li>

 * </ol>

 */

public abstract class SRPKey

    implements Key, Serializable

{

  /** The public, Germaine prime, shared modulus. */

  protected final BigInteger N;

  /** The generator. */

  protected final BigInteger g;

  protected SRPKey(BigInteger N, BigInteger g)

  {

    super();

    this.N = N;

    this.g = g;

  }

  /**

   * Returns the standard algorithm name for this key.

   *

   * @return the standard algorithm name for this key.

   */

  public String getAlgorithm()

  {

    return Registry.SRP_KPG;

  }

  /** @deprecated see getEncoded(int). */

  public byte[] getEncoded()

  {

    return getEncoded(IKeyPairCodec.RAW_FORMAT);

  }

  /**

   * Returns {@link Registry#RAW_ENCODING_SHORT_NAME} which is the sole format

   * supported for this type of keys.

   *

   * @return {@link Registry#RAW_ENCODING_SHORT_NAME} ALWAYS.

   */

  public String getFormat()

  {

    return Registry.RAW_ENCODING_SHORT_NAME;

  }

  /**

   * Returns the public shared modulus.

   *

   * @return <code>N</code>.

   */

  public BigInteger getN()

  {

    return N;

  }

  /**

   * Returns the generator.

   *

   * @return <code>g</code>.

   */

  public BigInteger getG()

  {

    return g;

  }

  /**

   * Returns <code>true</code> if the designated object is an instance of

   * <code>SRPKey</code> and has the same SRP parameter values as this one.

   *

   * @param obj the other non-null SRP 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 SRPKey))

      return false;

    SRPKey that = (SRPKey) obj;

    return N.equals(that.getN()) && g.equals(that.getG());

  }

  public abstract byte[] getEncoded(int format);

}