Save This Page
Home » openjdk-7 » java » security » [javadoc | source]
java.security
public class: KeyFactory [javadoc | source]
java.lang.Object
   java.security.KeyFactory
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);

Every implementation of the Java platform is required to support the following standard KeyFactory algorithms:

These algorithms are described in the KeyFactory section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.
Constructor:
 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 from java.security.KeyFactory Summary:
generatePrivate,   generatePublic,   getAlgorithm,   getInstance,   getInstance,   getInstance,   getKeySpec,   getProvider,   translateKey
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.security.KeyFactory Detail:
 public final PrivateKey generatePrivate(KeySpec keySpec) throws InvalidKeySpecException 
    Generates a private key object from the provided key specification (key material).
 public final PublicKey generatePublic(KeySpec keySpec) throws InvalidKeySpecException 
    Generates a public key object from the provided key specification (key material).
 public final String getAlgorithm() 
    Gets the name of the algorithm associated with this KeyFactory.
 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 Security.getProviders() method.

 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 Security.getProviders() method.

 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.

 public final T getKeySpec(Key key,
    Class<T> 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.
 public final Provider getProvider() 
    Returns the provider of this key factory object.
 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.