/* GnuDHKey.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
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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.

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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
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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.key.dh;

import gnu.java.security.Registry;
import gnu.java.security.action.GetPropertyAction;
import gnu.java.security.util.FormatUtil;

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

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

/**
 * 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>
 * 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>
 * Reference:
 * <ol>
 * <li><a href="http://www.ietf.org/rfc/rfc2631.txt">Diffie-Hellman Key
 * Agreement Method</a><br>
 * Eric Rescorla.</li>
 * </ol>
 */
public abstract class GnuDHKey
    implements Key, DHKey
{
  /** 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;
  /**
   * Identifier of the default encoding format to use when externalizing the key
   * material.
   */
  protected final int defaultFormat;
  /** String representation of this key. Cached for speed. */
  private transient String str;

  /**
   * Trivial protected constructor.
   * 
   * @param defaultFormat the identifier of the encoding format to use by
   *          default when externalizing the key.
   * @param q a prime divisor of p-1.
   * @param p the public prime.
   * @param g the generator of the group.
   */
  protected GnuDHKey(int defaultFormat, BigInteger q, BigInteger p, BigInteger g)
  {
    super();

    this.defaultFormat = defaultFormat <= 0 ? Registry.RAW_ENCODING_ID
                                            : defaultFormat;
    this.q = q;
    this.p = p;
    this.g = g;
  }

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

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

  /** @deprecated see getEncoded(int). */
  public byte[] getEncoded()
  {
    return getEncoded(defaultFormat);
  }

  public String getFormat()
  {
    return FormatUtil.getEncodingShortName(defaultFormat);
  }

  public BigInteger getQ()
  {
    return q;
  }

  /**
   * 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.
   * 
   * @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());
  }

  public String toString()
  {
    if (str == null)
      {
        String ls = (String) AccessController.doPrivileged
            (new GetPropertyAction("line.separator"));
        StringBuilder sb = new StringBuilder(ls)
            .append("defaultFormat=").append(defaultFormat).append(",").append(ls);
        if (q == null)
          sb.append("q=null,");
        else
          sb.append("q=0x").append(q.toString(16)).append(",");
        sb.append(ls).append("p=0x").append(p.toString(16)).append(",").append(ls)
            .append("g=0x").append(g.toString(16));
        str = sb.toString();
      }
    return str;
  }

  public abstract byte[] getEncoded(int format);
}