JavaTM 2 Platform
Std. Ed. v1.3.1

java.security
Class KeyFactory

java.lang.Object
  |
  +--java.security.KeyFactory

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);
 

Since:
1.2
See Also:
Key, PublicKey, PrivateKey, KeySpec, DSAPublicKeySpec, X509EncodedKeySpec

Constructor Summary
protected KeyFactory(KeyFactorySpi keyFacSpi, Provider provider, String algorithm)
          Creates a KeyFactory object.
 
Method Summary
 PrivateKey generatePrivate(KeySpec keySpec)
          Generates a private key object from the provided key specification (key material).
 PublicKey generatePublic(KeySpec keySpec)
          Generates a public key object from the provided key specification (key material).
 String getAlgorithm()
          Gets the name of the algorithm associated with this KeyFactory.
static KeyFactory getInstance(String algorithm)
          Generates a KeyFactory object that implements the specified digest algorithm.
static KeyFactory getInstance(String algorithm, String provider)
          Generates a KeyFactory object for the specified algorithm from the specified provider.
 KeySpec getKeySpec(Key key, Class keySpec)
          Returns a specification (key material) of the given key object.
 Provider getProvider()
          Returns the provider of this key factory object.
 Key translateKey(Key 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

getInstance

public static KeyFactory getInstance(String algorithm)
                              throws NoSuchAlgorithmException
Generates a KeyFactory object that implements the specified digest algorithm. If the default provider package provides an implementation of the requested digest algorithm, an instance of KeyFactory containing that implementation is returned. If the algorithm is not available in the default package, other packages are searched.
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:
a KeyFactory object for the specified algorithm.
Throws:
NoSuchAlgorithmException - if the requested algorithm is not available in the default provider package or any of the other provider packages that were searched.

getInstance

public static KeyFactory getInstance(String algorithm,
                                     String provider)
                              throws NoSuchAlgorithmException,
                                     NoSuchProviderException
Generates a KeyFactory object for the specified algorithm from the specified provider.
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:
a KeyFactory object for the specified algorithm.
Throws:
NoSuchAlgorithmException - if the algorithm is not available from the specified provider.
NoSuchProviderException - if the provider has not been configured.
See Also:
Provider

getProvider

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

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

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.

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.

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).

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.

JavaTM 2 Platform
Std. Ed. v1.3.1

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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