/* DSSKey.java -- 
   Copyright 2001, 2002, 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

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package gnu.java.security.key.dss;

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

import java.math.BigInteger;
import java.security.Key;
import java.security.interfaces.DSAKey;
import java.security.interfaces.DSAParams;
import java.security.spec.DSAParameterSpec;

/**
 * <p>A base asbtract class for both public and private DSS (Digital Signature
 * Standard) keys. It encapsulates the three DSS numbers: <code>p</code>,
 * <code>q</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>
 *
 * @version $Revision: 1.4 $
 * @see DSSPrivateKey#getEncoded
 * @see DSSPublicKey#getEncoded
 */
public abstract class DSSKey implements Key, DSAKey
{
  // Constants and variables
  // -------------------------------------------------------------------------

  /**
   * A prime modulus, where <code>2<sup>L-1</sup> &lt; p &lt; 2<sup>L</sup></code>
   * for <code>512 &lt;= L &lt;= 1024</code> and <code>L</code> a multiple of
   * <code>64</code>.
   */
  protected final BigInteger p;

  /**
   * A prime divisor of <code>p - 1</code>, where <code>2<sup>159</sup> &lt; q
   * &lt; 2<sup>160</sup></code>.
   */
  protected final BigInteger q;

  /**
   * <code>g = h<sup>(p-1)</sup>/q mod p</code>, where <code>h</code> is any
   * integer with <code>1 &lt; h &lt; p - 1</code> such that <code>h<sup>
   * (p-1)</sup>/q mod p > 1</code> (<code>g</code> has order <code>q mod p
   * </code>).
   */
  protected final BigInteger g;

  /**
   * Identifier of the default encoding format to use when externalizing the
   * key material.
   */
  protected final int defaultFormat;

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

  /**
   * Trivial protected constructor.
   * 
   * @param defaultFormat the identifier of the encoding format to use by
   * default when externalizing the key.
   * @param p the DSS parameter <code>p</code>.
   * @param q the DSS parameter <code>q</code>.
   * @param g the DSS parameter <code>g</code>.
   */
  protected DSSKey(int defaultFormat, BigInteger p, BigInteger q, BigInteger g)
  {
    super();

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

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

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

  // java.security.interfaces.DSAKey interface implementation ----------------

  public DSAParams getParams()
  {
    return new DSAParameterSpec(p, q, g);
  }

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

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

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

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

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

  /**
   * <p>Returns <code>true</code> if the designated object is an instance of
   * {@link DSAKey} and has the same DSS (Digital Signature Standard) parameter
   * values as this one.</p>
   *
   * @param obj the other non-null DSS 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 DSAKey))
      {
        return false;
      }
    DSAKey that = (DSAKey) obj;
    return p.equals(that.getParams().getP())
           && q.equals(that.getParams().getQ())
           && g.equals(that.getParams().getG());
  }

  // abstract methods to be implemented by subclasses ------------------------

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