/*

 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.security;

import java.security.spec.KeySpec;

import java.security.spec.InvalidKeySpecException;

/**

 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)

 * for the {@code KeyFactory} class.

 * All the abstract methods in this class must be implemented by each

 * cryptographic service provider who wishes to supply the implementation

 * of a key factory for a particular algorithm.

 *

 * <P> Key factories are used to convert <I>keys</I> (opaque

 * cryptographic keys of type {@code Key}) into <I>key specifications</I>

 * (transparent representations of the underlying key material), and vice

 * versa.

 *

 * <P> Key factories are bi-directional. That is, they allow you to build an

 * opaque key object from a given key specification (key material), or to

 * retrieve the underlying key material of a key object in a suitable format.

 *

 * <P> Multiple compatible key specifications may exist for the same key.

 * For example, a DSA public key may be specified using

 * {@code DSAPublicKeySpec} or

 * {@code X509EncodedKeySpec}. A key factory can be used to translate

 * between compatible key specifications.

 *

 * <P> A provider should document all the key specifications supported by its

 * key factory.

 *

 * @author Jan Luehe

 *

 *

 * @see KeyFactory

 * @see Key

 * @see PublicKey

 * @see PrivateKey

 * @see java.security.spec.KeySpec

 * @see java.security.spec.DSAPublicKeySpec

 * @see java.security.spec.X509EncodedKeySpec

 *

 * @since 1.2

 */

public abstract class KeyFactorySpi {

    /**

     * Generates a public key object from the provided key

     * specification (key material).

     *

     * @param keySpec the specification (key material) of the public key.

     *

     * @return the public key.

     *

     * @exception InvalidKeySpecException if the given key specification

     * is inappropriate for this key factory to produce a public key.

     */

    protected abstract PublicKey engineGeneratePublic(KeySpec keySpec)

        throws InvalidKeySpecException;

    /**

     * Generates a private key object from the provided key

     * specification (key material).

     *

     * @param keySpec the specification (key material) of the private key.

     *

     * @return the private key.

     *

     * @exception InvalidKeySpecException if the given key specification

     * is inappropriate for this key factory to produce a private key.

     */

    protected abstract PrivateKey engineGeneratePrivate(KeySpec keySpec)

        throws InvalidKeySpecException;

    /**

     * Returns a specification (key material) of the given key

     * object.

     * {@code keySpec} identifies the specification class in which

     * the key material should be returned. It could, for example, be

     * {@code DSAPublicKeySpec.class}, to indicate that the

     * key material should be returned in an instance of the

     * {@code DSAPublicKeySpec} class.

     *

     * @param <T> the type of the key specification to be returned

     *

     * @param key the key.

     *

     * @param keySpec the specification class in which

     * the key material should be returned.

     *

     * @return the underlying key specification (key material) in an instance

     * of the requested specification class.

     * @exception InvalidKeySpecException if the requested key specification is

     * inappropriate for the given key, or the given key cannot be dealt with

     * (e.g., the given key has an unrecognized format).

     */

    protected abstract <T extends KeySpec>

        T engineGetKeySpec(Key key, Class<T> keySpec)

        throws InvalidKeySpecException;

    /**

     * Translates a key object, whose provider may be unknown or

     * potentially untrusted, into a corresponding key object of this key

     * factory.

     *

     * @param key the key whose provider is unknown or untrusted.

     *

     * @return the translated key.

     *

     * @exception InvalidKeyException if the given key cannot be processed

     * by this key factory.

     */

    protected abstract Key engineTranslateKey(Key key)

        throws InvalidKeyException;

}