/*
* @(#)KeyFactory.java 1.28 02/05/07
*
* Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program 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.
*
* This program 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 at /legal/license.txt).
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*
*/
package java.security;
import java.security.spec.KeySpec;
import java.security.spec.InvalidKeySpecException;
/**
* Key factories are used to convert <I>keys</I> (opaque
* cryptographic keys of type <code>Key</code>) 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</code> or
* <code>X509EncodedKeySpec</code>. A key factory can be used to translate
* between compatible key specifications.
*
* <P> The following is an example of how to use a key factory in order to
* instantiate a DSA public key from its encoding.
* Assume Alice has received a digital signature from Bob.
* Bob also sent her his public key (in encoded format) to verify
* his signature. Alice then performs the following actions:
*
* <pre>
* X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec(bobEncodedPubKey);
* KeyFactory keyFactory = KeyFactory.getInstance("DSA");
* PublicKey bobPubKey = keyFactory.generatePublic(bobPubKeySpec);
* Signature sig = Signature.getInstance("DSA");
* sig.initVerify(bobPubKey);
* sig.update(data);
* sig.verify(signature);
* </pre>
*
* @author Jan Luehe
*
* @version 1.28, 05/07/02
*
* @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 class KeyFactory {
// The algorithm associated with this key factory
private String algorithm;
// The provider
private Provider provider;
// The provider implementation (delegate)
private KeyFactorySpi keyFacSpi;
/**
* Creates a KeyFactory object.
*
* @param keyFacSpi the delegate
* @param provider the provider
* @param algorithm the name of the algorithm
* to associate with this <tt>KeyFactory</tt>
*/
protected KeyFactory(KeyFactorySpi keyFacSpi, Provider provider,
String algorithm) {
this.keyFacSpi = keyFacSpi;
this.provider = provider;
this.algorithm = algorithm;
}
/**
* Generates a KeyFactory object that implements the specified
* algorithm. If the default provider package
* provides an implementation of the requested algorithm,
* an instance of KeyFactory containing that implementation is returned.
* If the algorithm is not available in the default
* package, other packages are searched.
*
* @param algorithm the name of the requested key algorithm.
* See Appendix A in the <a href=
* "../../../guide/security/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard algorithm names.
*
* @return a KeyFactory object for the specified algorithm.
*
* @exception NoSuchAlgorithmException if the requested algorithm is
* not available in the default provider package or any of the other
* provider packages that were searched.
*/
public static KeyFactory getInstance(String algorithm)
throws NoSuchAlgorithmException {
try {
Object[] objs = Security.getImpl(algorithm, "KeyFactory",
(String)null);
return new KeyFactory((KeyFactorySpi)objs[0],
(Provider)objs[1],
algorithm);
} catch(NoSuchProviderException e) {
throw new NoSuchAlgorithmException(algorithm + " not found");
}
}
/**
* Generates a KeyFactory object for the specified algorithm from the
* specified provider.
*
* @param algorithm the name of the requested key algorithm.
* See Appendix A in the <a href=
* "../../../guide/security/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard algorithm names.
*
* @param provider the name of the provider.
*
* @return a KeyFactory object for the specified algorithm.
*
* @exception NoSuchAlgorithmException if the algorithm is
* not available from the specified provider.
*
* @exception NoSuchProviderException if the provider has not been
* configured.
*
* @exception IllegalArgumentException if the provider name is null
* or empty.
*
* @see Provider
*/
public static KeyFactory getInstance(String algorithm, String provider)
throws NoSuchAlgorithmException, NoSuchProviderException
{
if (provider == null || provider.length() == 0)
throw new IllegalArgumentException("missing provider");
Object[] objs = Security.getImpl(algorithm, "KeyFactory", provider);
return new KeyFactory((KeyFactorySpi)objs[0], (Provider)objs[1],
algorithm);
}
/**
* Generates a KeyFactory object for the specified algorithm from the
* specified provider. Note: the <code>provider</code> doesn't have
* to be registered.
*
* @param algorithm the name of the requested key algorithm.
* See Appendix A in the <a href=
* "../../../guide/security/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard algorithm names.
*
* @param provider the provider.
*
* @return a KeyFactory object for the specified algorithm.
*
* @exception NoSuchAlgorithmException if the algorithm is
* not available from the specified provider.
*
* @exception IllegalArgumentException if the <code>provider</code> is
* null.
*
* @see Provider
*
* @since 1.4
*/
public static KeyFactory getInstance(String algorithm, Provider provider)
throws NoSuchAlgorithmException
{
if (provider == null)
throw new IllegalArgumentException("missing provider");
Object[] objs = Security.getImpl(algorithm, "KeyFactory", provider);
return new KeyFactory((KeyFactorySpi)objs[0], (Provider)objs[1],
algorithm);
}
/**
* Returns the provider of this key factory object.
*
* @return the provider of this key factory object
*/
public final Provider getProvider() {
return this.provider;
}
/**
* Gets the name of the algorithm
* associated with this <tt>KeyFactory</tt>.
*
* @return the name of the algorithm associated with this
* <tt>KeyFactory</tt>
*/
public final String getAlgorithm() {
return this.algorithm;
}
/**
* 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.
*/
public final PublicKey generatePublic(KeySpec keySpec)
throws InvalidKeySpecException {
return keyFacSpi.engineGeneratePublic(keySpec);
}
/**
* 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.
*/
public final PrivateKey generatePrivate(KeySpec keySpec)
throws InvalidKeySpecException {
return keyFacSpi.engineGeneratePrivate(keySpec);
}
/**
* Returns a specification (key material) of the given key object.
* <code>keySpec</code> identifies the specification class in which
* the key material should be returned. It could, for example, be
* <code>DSAPublicKeySpec.class</code>, to indicate that the
* key material should be returned in an instance of the
* <code>DSAPublicKeySpec</code> class.
*
* @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 processed
* (e.g., the given key has an unrecognized algorithm or format).
*/
public final KeySpec getKeySpec(Key key, Class keySpec)
throws InvalidKeySpecException {
return keyFacSpi.engineGetKeySpec(key, keySpec);
}
/**
* 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.
*/
public final Key translateKey(Key key) throws InvalidKeyException {
return keyFacSpi.engineTranslateKey(key);
}
}