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           Returns           Generates a KeyFactory object that converts public/private keys of implements the specified algorithm.
static  KeyFactory	getInstance ( String  algorithm, Provider           Returns           Generates a KeyFactory object that converts public/private keys of for the specified algorithm. algorithm from the specified provider.
static  KeyFactory	getInstance ( String  algorithm, String           Returns           Generates a KeyFactory object that converts public/private keys of for the specified algorithm. algorithm from the specified provider.
<T extends KeySpec > T	getKeySpec ( Key  key, Class <T> 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

getInstance

public static KeyFactory getInstance(String algorithm)
                              throws NoSuchAlgorithmException

Returns a KeyFactory object that converts public/private keys of the specified 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.

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.

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. a KeyFactory object for the specified algorithm.

Throws:

NoSuchAlgorithmException - if no Provider supports a KeyFactorySpi implementation for the specified algorithm.

See Also:

Provider - 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

Returns a KeyFactory object that converts public/private keys of the specified algorithm. Generates a KeyFactory object for the specified algorithm from the specified provider.

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.

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. a KeyFactory object for the specified algorithm.

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. - if the provider has not been configured.

IllegalArgumentException - if the provider name is null or empty.

See Also:

Provider

getInstance

public static KeyFactory getInstance(String algorithm,
                                     Provider provider)
                              throws NoSuchAlgorithmException

Returns a KeyFactory object that converts public/private keys of the specified algorithm. Generates a KeyFactory object for the specified algorithm from the specified provider. Note: the provider doesn't have to be registered.

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. a KeyFactory object for the specified algorithm.

Throws:

NoSuchAlgorithmException - if a KeyFactorySpi implementation for the specified algorithm is not available from the specified Provider object. provider.

IllegalArgumentException - if the specified provider is null.

Since:

1.4

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 <T extends KeySpec> 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.

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.