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package java.security;

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


This class defines the Service Provider Interface (SPI) for the 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. 
 Key factories are used to convert keys (opaque cryptographic keys of type Key) into key specifications
(transparent representations of the underlying key material), and vice
versa.

 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.

 Multiple compatible key specifications may exist for the same key. For example, a DSA public key may be specified using DSAPublicKeySpec or X509EncodedKeySpec. A key factory can be used to translate between compatible key specifications. 
 A provider should document all the key specifications supported by its
key factory.

Author:Jan Luehe
See Also:
Since:1.2
/**
 * 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).

Params:
  • keySpec – the specification (key material) of the public key.
Throws:
  • InvalidKeySpecException – if the given key specification
is inappropriate for this key factory to produce a public key.
Returns:the public key.
/**
     * 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).

Params:
  • keySpec – the specification (key material) of the private key.
Throws:
  • InvalidKeySpecException – if the given key specification
is inappropriate for this key factory to produce a private key.
Returns:the private key.
/**
     * 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. keySpec identifies the specification class in which the key material should be returned. It could, for example, be DSAPublicKeySpec.class, to indicate that the key material should be returned in an instance of the DSAPublicKeySpec class. 
Params:
  • key – the key.
  • keySpec – the specification class in which
the key material should be returned.
Type parameters:
  • <T> – the type of the key specification to be returned
Throws:
  • 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).
Returns:the underlying key specification (key material) in an instance
of the requested specification class.
/**
     * 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.

Params:
  • key – the key whose provider is unknown or untrusted.
Throws:
Returns:the translated key.
/**
     * 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;

}