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java.security
class KeyFactory

java.lang.Object extended by java.security.KeyFactory

Most common way to construct:

KeyFactory keyFactory = KeyFactory.getInstance("DSA");

Based on 142 examples


public class KeyFactory
extends Object

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.

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:

 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);
 


Constructor Summary
protected
KeyFactory(KeyFactorySpi keyFacSpi, Provider provider, String algorithm)

          Creates a KeyFactory object.
 
Method Summary
 PrivateKey

          Generates a private key object from the provided key specification (key material).
 PublicKey

          Generates a public key object from the provided key specification (key material).
 String

          Gets the name of the algorithm associated with this KeyFactory.
static KeyFactory
getInstance(String algorithm)

          Returns a KeyFactory object that converts public/private keys of the specified algorithm.
static KeyFactory
getInstance(String algorithm, Provider provider)

          Returns a KeyFactory object that converts public/private keys of the specified algorithm.
static KeyFactory
getInstance(String algorithm, String provider)

          Returns a KeyFactory object that converts public/private keys of the specified algorithm.
 KeySpec
getKeySpec(Key key, Class keySpec)

          Returns a specification (key material) of the given key object.
 Provider

          Returns the provider of this key factory object.
 Key

          Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

KeyFactory

protected KeyFactory(KeyFactorySpi keyFacSpi,
                     Provider provider,
                     String algorithm)
Creates a KeyFactory object.

Parameters:
keyFacSpi - the delegate
provider - the provider
algorithm - the name of the algorithm to associate with this KeyFactory
Method Detail

generatePrivate

public final PrivateKey generatePrivate(KeySpec keySpec)
                                 throws InvalidKeySpecException
Generates a private key object from the provided key specification (key material).

Parameters:
keySpec - the specification (key material) of the private key.
Returns:
the private key.
Throws:
InvalidKeySpecException - if the given key specification is inappropriate for this key factory to produce a private key.

generatePublic

public final PublicKey generatePublic(KeySpec keySpec)
                               throws InvalidKeySpecException
Generates a public key object from the provided key specification (key material).

Parameters:
keySpec - the specification (key material) of the public key.
Returns:
the public key.
Throws:
InvalidKeySpecException - if the given key specification is inappropriate for this key factory to produce a public key.

getAlgorithm

public final String getAlgorithm()
Gets the name of the algorithm associated with this KeyFactory.

Returns:
the name of the algorithm associated with this KeyFactory

getInstance

public static KeyFactory getInstance(String algorithm)
                              throws NoSuchAlgorithmException
Returns a KeyFactory object that converts public/private keys of the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyFactory object encapsulating the KeyFactorySpi implementation from the first Provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the {@link Security#getProviders() Security.getProviders()} method.

Parameters:
algorithm - the name of the requested key algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard algorithm names.
Returns:
the new KeyFactory object.
Throws:
NoSuchAlgorithmException - if no Provider supports a KeyFactorySpi implementation for the specified algorithm.

getInstance

public static KeyFactory getInstance(String algorithm,
                                     Provider provider)
                              throws NoSuchAlgorithmException
Returns a KeyFactory object that converts public/private keys of the specified algorithm.

A new KeyFactory object encapsulating the KeyFactorySpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

Parameters:
algorithm - the name of the requested key algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard algorithm names.
provider - the provider.
Returns:
the new KeyFactory object.
Throws:
NoSuchAlgorithmException - if a KeyFactorySpi implementation for the specified algorithm is not available from the specified Provider object.

getInstance

public static KeyFactory getInstance(String algorithm,
                                     String provider)
                              throws NoSuchAlgorithmException,
                                     NoSuchProviderException
Returns a KeyFactory object that converts public/private keys of the specified algorithm.

A new KeyFactory object encapsulating the KeyFactorySpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the {@link Security#getProviders() Security.getProviders()} method.

Parameters:
algorithm - the name of the requested key algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard algorithm names.
provider - the name of the provider.
Returns:
the new KeyFactory object.
Throws:
NoSuchAlgorithmException - if a KeyFactorySpi implementation for the specified algorithm is not available from the specified provider.
NoSuchProviderException - if the specified provider is not registered in the security provider list.

getKeySpec

public final KeySpec getKeySpec(Key key,
                                Class 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.

Parameters:
key - the key.
keySpec - the specification class in which the key material should be returned.
Returns:
the underlying key specification (key material) in an instance of the requested specification class.
Throws:
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).

getProvider

public final Provider getProvider()
Returns the provider of this key factory object.

Returns:
the provider of this key factory object

translateKey

public final Key translateKey(Key key)
                       throws InvalidKeyException
Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.

Parameters:
key - the key whose provider is unknown or untrusted.
Returns:
the translated key.
Throws:
InvalidKeyException - if the given key cannot be processed by this key factory.


This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.
This page displays the Jadeite version of the documention, which is derived from the offical documentation that contains this copyright notice:
Copyright 2008 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
The official Sun™ documentation can be found here at http://java.sun.com/javase/6/docs/api/.