javax.crypto
Class SecretKeyFactory

java.lang.Object
  javax.crypto.SecretKeyFactory

public class SecretKeyFactory
extends Object

This class represents a factory for secret keys.

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. Secret key factories operate only on secret (symmetric) keys.

Key factories are bi-directional, i.e., they allow 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.

Application developers should refer to their provider's documentation to find out which key specifications are supported by the generateSecret and getKeySpec methods. For example, the DES secret-key factory supplied by the "SunJCE" provider supports DESKeySpec as a transparent representation of DES keys, and that provider's secret-key factory for Triple DES keys supports DESedeKeySpec as a transparent representation of Triple DES keys.

Version:

$Id: SecretKeyFactory.java 1913 2007-08-08 02:41:53Z jpeters $

Author:

Patric Kabus, Jan Peters

Field Summary

private String	algorithm_ The secret-key algorithm used by this instance.
private SecretKeyFactorySpi	keyFacSpi_ The key factory used by this instance.
private Provider	provider_ The provider used by this instance.

Constructor Summary

protected

SecretKeyFactory(SecretKeyFactorySpi keyFacSpi, Provider provider, String algorithm) Creates a SecretKeyFactory object.

Method Summary

SecretKey	generateSecret(KeySpec keySpec) Generates a SecretKey object from the provided key specification (key material).
String	getAlgorithm() Returns the algorithm name of this SecretKeyFactory object.
static SecretKeyFactory	getInstance(String algorithm) Generates a SecretKeyFactory object for the specified secret-key algorithm.
static SecretKeyFactory	getInstance(String algorithm, Provider provider) Generates a SecretKeyFactory object for the specified secret-key algorithm from the specified provider.
static SecretKeyFactory	getInstance(String algorithm, String provider) Generates a SecretKeyFactory object for the specified secret-key algorithm from the specified provider.
KeySpec	getKeySpec(SecretKey key, Class keySpec) Returns a specification (key material) of the given key object in the requested format.
Provider	getProvider() Returns the provider of this SecretKeyFactory object.
SecretKey	translateKey(SecretKey key) Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this secret-key factory.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

keyFacSpi_

private SecretKeyFactorySpi keyFacSpi_

The key factory used by this instance.

provider_

private Provider provider_

The provider used by this instance.

algorithm_

private String algorithm_

The secret-key algorithm used by this instance.

Constructor Detail

SecretKeyFactory

protected SecretKeyFactory(SecretKeyFactorySpi keyFacSpi,
                           Provider provider,
                           String algorithm)

Creates a SecretKeyFactory object.

Parameters:

keyFacSpi - the delegate.

provider - the provider.

algorithm - the secret-key algorithm.

Method Detail

getInstance

public static final SecretKeyFactory getInstance(String algorithm)
                                          throws NoSuchAlgorithmException

Generates a SecretKeyFactory object for the specified secret-key algorithm. If the default provider package provides an implementation of the requested factory, an instance of SecretKeyFactory containing that implementation is returned. If the requested factory is not available in the default provider package, other provider packages are searched.

Parameters:

algorithm - the standard name of the requested secret-key algorithm. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.

Returns:

a SecretKeyFactory object for the specified secret-key algorithm.

Throws:

NoSuchAlgorithmException - if a secret-key factory for the specified algorithm is not available in the default provider package or any of the other provider packages that were searched.

NullPointerException - if the specified algorithm is null.

getInstance

public static final SecretKeyFactory getInstance(String algorithm,
                                                 String provider)
                                          throws NoSuchAlgorithmException,
                                                 NoSuchProviderException

Generates a SecretKeyFactory object for the specified secret-key algorithm from the specified provider.

Parameters:

algorithm - the standard name of the requested secret-key algorithm. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.

provider - the name of the provider

Returns:

a SecretKeyFactory object for the specified secret-key algorithm.

Throws:

NoSuchAlgorithmException - if a secret-key factory for the specified algorithm is not available from the specified provider.

NoSuchProviderException - if the specified provider has not been configured.

IllegalArgumentException - if the provider is null.

NullPointerException - if the specified algorithm is null.

getInstance

public static final SecretKeyFactory getInstance(String algorithm,
                                                 Provider provider)
                                          throws NoSuchAlgorithmException,
                                                 NoSuchProviderException

Generates a SecretKeyFactory object for the specified secret-key algorithm from the specified provider.

Parameters:

algorithm - the standard name of the requested secret-key algorithm. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.

provider - the provider

Returns:

a SecretKeyFactory object for the specified secret-key algorithm.

Throws:

NoSuchAlgorithmException - if a secret-key factory for the specified algorithm is not available from the specified provider.

IllegalArgumentException - if the provider is null.

NullPointerException - if the specified algorithm is null.

NoSuchProviderException

getProvider

public final Provider getProvider()

Returns the provider of this SecretKeyFactory object.

Returns:

the provider of this SecretKeyFactory object.

getAlgorithm

public final String getAlgorithm()

Returns the algorithm name of this SecretKeyFactory object. This is the same name that was specified in one of the getInstance calls that created this SecretKeyFactory object.

Returns:

the algorithm name of this SecretKeyFactory object.

generateSecret

public final SecretKey generateSecret(KeySpec keySpec)
                               throws InvalidKeySpecException

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

Parameters:

keySpec - the specification (key material) of the secret key.

Returns:

the secret key.

Throws:

InvalidKeySpecException - if the given key specification is inappropriate for this secret-key factory to produce a secret key.

getKeySpec

public final KeySpec getKeySpec(SecretKey key,
                                Class keySpec)
                         throws InvalidKeySpecException

Returns a specification (key material) of the given key object in the requested format.

Parameters:

key - the key.

keySpec - the requested format in which the key material shall be returned.

Returns:

the underlying key specification (key material) in the requested format.

Throws:

InvalidKeySpecException - if the requested key specification is inappropriate for the given key (e.g., the algorithms associated with key and keySpec do not match, or key references a key on a cryptographic hardware device whereas keySpec is the specification of a software-based key), or the given key cannot be dealt with (e.g., the given key has an algorithm or format not supported by this secret-key factory).

translateKey

public final SecretKey translateKey(SecretKey key)
                             throws InvalidKeyException

Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this secret-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 secret-key factory.