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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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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;

}