/* KeyFactorySpi.java --- Key Factory Service Provider Interface
   Copyright (C) 1999, 2004  Free Software Foundation, Inc.

This file is part of GNU Classpath.

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package java.security;

import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;

/**
 * KeyFactorySpi is the Service Provider Interface (SPI) for the 
 * KeyFactory class. This is the interface for providers to 
 * supply to implement a key factory for an algorithm.
 *
 * Key factories are used to convert keys (opaque cryptographic 
 * keys of type Key) into key specifications (transparent 
 * representations of the underlying key material).
 *
 * Key factories are bi-directional. They allow a key class 
 * to be converted into a key specification (key material) and
 * back again.
 *
 * For example DSA public keys can be specified as 
 * DSAPublicKeySpec or X509EncodedKeySpec. The key factory
 * translate these key specifications. 
 *
 * @since JDK 1.2
 * @author Mark Benvenuto
 */
public abstract class KeyFactorySpi
{
  /**
   * Constucts a new KeyFactorySpi.
   */
  public KeyFactorySpi()
  {
  }

  /**
   * Generates a public key from the provided key specification.
   *
   * @param keySpec key specification
   *
   * @return the public key
   *
   * @throws InvalidKeySpecException invalid key specification for
   * this key factory to produce a public key
   */
  protected abstract PublicKey engineGeneratePublic(KeySpec keySpec)
    throws InvalidKeySpecException;


  /**
   * Generates a private key from the provided key specification.
   *
   * @param keySpec key specification
   *
   * @return the private key
   *
   * @throws InvalidKeySpecException invalid key specification for
   * this key factory to produce a private key
   */
  protected abstract PrivateKey engineGeneratePrivate(KeySpec keySpec)
    throws InvalidKeySpecException;

  /**
   * Returns a key specification for the given key. keySpec 
   * identifies the specification class to return the key 
   * material in.
   *
   * @param key the key
   * @param keySpec the specification class to return the 
   * key material in.
   *
   * @return the key specification in an instance of the requested
   * specification class
   *
   * @throws InvalidKeySpecException the requested key specification
   * is inappropriate for this key or the key is 
   * unrecognized.
   */
  protected abstract <T extends KeySpec> T engineGetKeySpec(Key key,
                                                            Class<T> keySpec)
    throws InvalidKeySpecException;


  /**
   * Translates the key from an unknown or untrusted provider
   * into a key for this key factory.
   *
   * @param key key from an unknown or untrusted provider
   *
   * @return the translated key
   *
   * @throws InvalidKeyException if the key cannot be 
   * processed by this key factory
   */
  protected abstract Key engineTranslateKey(Key key)
    throws InvalidKeyException;
}