/* KeyPairGenerator.java --- Key Pair Generator Class
   Copyright (C) 1999, 2002, 2003, 2004, 2005  Free Software Foundation, Inc.

This file is 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, 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.

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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
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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
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.security;

import gnu.java.security.Engine;

import java.security.spec.AlgorithmParameterSpec;

/**
 * <code>KeyPairGenerator</code> is a class used to generate key-pairs for a
 * security algorithm.
 * 
 * <p>The <code>KeyPairGenerator</code> is created with the
 * <code>getInstance()</code> Factory methods. It is used to generate a pair of
 * public and private keys for a specific algorithm and associate this key-pair
 * with the algorithm parameters it was initialized with.</p>
 *
 * @see KeyPair
 * @see AlgorithmParameterSpec
 * @author Mark Benvenuto
 * @author Casey Marshall
 */
public abstract class KeyPairGenerator extends KeyPairGeneratorSpi
{
  /** The service name for key pair generators. */
  private static final String KEY_PAIR_GENERATOR = "KeyPairGenerator";

  Provider provider;
  private String algorithm;

  /**
   * Constructs a new instance of <code>KeyPairGenerator</code>.
   * 
   * @param algorithm
   *          the algorithm to use.
   */
  protected KeyPairGenerator(String algorithm)
  {
    this.algorithm = algorithm;
    this.provider = null;
  }

  /**
   * Returns the name of the algorithm used.
   * 
   * @return the name of the algorithm used.
   */
  public String getAlgorithm()
  {
    return algorithm;
  }

  /**
   * Returns a new instance of <code>KeyPairGenerator</code> which generates
   * key-pairs for the specified algorithm.
   * 
   * @param algorithm
   *          the name of the algorithm to use.
   * @return a new instance repesenting the desired algorithm.
   * @throws NoSuchAlgorithmException
   *           if the algorithm is not implemented by any provider.
   */
  public static KeyPairGenerator getInstance(String algorithm)
    throws NoSuchAlgorithmException
  {
    Provider[] p = Security.getProviders();
    for (int i = 0; i < p.length; i++)
      {
        try
          {
            return getInstance(algorithm, p[i]);
	  }
	catch (NoSuchAlgorithmException e)
	  {
	    // Ignored.
	  }
      }

    throw new NoSuchAlgorithmException(algorithm);
  }

  /**
   * Returns a new instance of <code>KeyPairGenerator</code> which generates
   * key-pairs for the specified algorithm from a named provider.
   * 
   * @param algorithm
   *          the name of the algorithm to use.
   * @param provider
   *          the name of a {@link Provider} to use.
   * @return a new instance repesenting the desired algorithm.
   * @throws NoSuchAlgorithmException
   *           if the algorithm is not implemented by the named provider.
   * @throws NoSuchProviderException
   *           if the named provider was not found.
   */
  public static KeyPairGenerator getInstance(String algorithm, String provider)
    throws NoSuchAlgorithmException, NoSuchProviderException
  {
    Provider p = Security.getProvider(provider);
    if (p == null)
      throw new NoSuchProviderException(provider);

    return getInstance(algorithm, p);
  }

  /**
   * Returns a new instance of <code>KeyPairGenerator</code> which generates
   * key-pairs for the specified algorithm from a designated {@link Provider}.
   * 
   * @param algorithm
   *          the name of the algorithm to use.
   * @param provider
   *          the {@link Provider} to use.
   * @return a new insatnce repesenting the desired algorithm.
   * @throws IllegalArgumentException
   *           if <code>provider</code> is <code>null</code>.
   * @throws NoSuchAlgorithmException
   *           if the algorithm is not implemented by the {@link Provider}.
   * @since 1.4
   * @see Provider
   */
  public static KeyPairGenerator getInstance(String algorithm, 
					     Provider provider)
    throws NoSuchAlgorithmException
  {
    if (provider == null)
      throw new IllegalArgumentException("Illegal provider");

    Object o = null;
    try
      {
        o = Engine.getInstance(KEY_PAIR_GENERATOR, algorithm, provider);
      }
    catch (java.lang.reflect.InvocationTargetException ite)
      {
	throw new NoSuchAlgorithmException(algorithm);
      }

    KeyPairGenerator result = null;
    if (o instanceof KeyPairGenerator)
      {
        result = (KeyPairGenerator) o;
        result.algorithm = algorithm;
      }
    else if (o instanceof KeyPairGeneratorSpi)
      result = new DummyKeyPairGenerator((KeyPairGeneratorSpi) o, algorithm);

    result.provider = provider;
    return result;
  }

  /**
   * Returns the {@link Provider} of this instance.
   * 
   * @return the {@link Provider} of this instance.
   */
  public final Provider getProvider()
  {
    return provider;
  }

  /**
   * Initializes this instance for the specified key size. Since no source of
   * randomness is specified, a default one will be used.
   * 
   * @param keysize
   *          the size of keys to use.
   */
  public void initialize(int keysize)
  {
    initialize(keysize, new SecureRandom());
  }

  /**
   * Initializes this instance for the specified key size and
   * {@link SecureRandom}.
   * 
   * @param keysize
   *          the size of keys to use.
   * @param random
   *          the {@link SecureRandom} to use.
   * @since 1.2
   */
  public void initialize(int keysize, SecureRandom random)
  {
  }

  /**
   * Initializes this instance with the specified
   * {@link AlgorithmParameterSpec}. Since no source of randomness is specified,
   * a default one will be used.
   * 
   * @param params
   *          the {@link AlgorithmParameterSpec} to use.
   * @throws InvalidAlgorithmParameterException
   *           if the designated specifications are invalid.
   * @since 1.2
   */
  public void initialize(AlgorithmParameterSpec params)
    throws InvalidAlgorithmParameterException
  {
    initialize(params, new SecureRandom());
  }

  /**
   * Initializes this instance with the specified {@link AlgorithmParameterSpec}
   * and {@link SecureRandom}.
   * 
   * @param params
   *          the {@link AlgorithmParameterSpec} to use.
   * @param random
   *          the {@link SecureRandom} to use.
   * @throws InvalidAlgorithmParameterException
   *           if the designated specifications are invalid.
   * @since 1.2
   */
  public void initialize(AlgorithmParameterSpec params, SecureRandom random)
    throws InvalidAlgorithmParameterException
  {
    super.initialize(params, random);
  }

  /**
   * Generates a new "DSA" {@link KeyPair} from the "GNU" security provider.
   * 
   * <p>This method generates a unique key-pair each time it is called.</p>
   * 
   * @return a new unique {@link KeyPair}.
   * @see #generateKeyPair()
   * @since 1.2
   */
  public final KeyPair genKeyPair()
  {
    try
      {
        return getInstance("DSA", "GNU").generateKeyPair();
      }
    catch (Exception e)
      {
        System.err.println("genKeyPair failed: " + e);
        e.printStackTrace();
        return null;
      }
  }

  /**
   * Generates a new "DSA" {@link KeyPair} from the "GNU" security provider.
   * 
   * <p>This method generates a unique key pair each time it is called.</p>
   * 
   * @return a new unique {@link KeyPair}.
   * @see #genKeyPair()
   */
  public KeyPair generateKeyPair()
  {
    return genKeyPair();
  }
}