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javax.crypto
Class SecretKeyFactory


java.lang.Object
  extended by 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.

Since:
1.4
See Also:
SecretKey , DESKeySpec , DESedeKeySpec , PBEKeySpec

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)
          Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
static  SecretKeyFactory getInstance ( String  algorithm, Provider  provider)
          Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
static  SecretKeyFactory getInstance ( String  algorithm, String  provider)
          Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
  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
 

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
Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new SecretKeyFactory object encapsulating the SecretKeyFactorySpi 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 standard name of the requested secret-key algorithm. See Appendix A in the Java Cryptography Architecture Reference Guide Java Cryptography Extension Reference Guide for information about standard algorithm names.
Returns:
the new SecretKeyFactory object.
Throws:
NullPointerException - if the specified algorithm is null.
NoSuchAlgorithmException - if no Provider supports a SecretKeyFactorySpi implementation for the specified algorithm.
See Also:
Provider

getInstance


public static final SecretKeyFactory getInstance(String algorithm,
                                                 String provider)
                                          throws NoSuchAlgorithmException,
                                                 NoSuchProviderException
Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.

A new SecretKeyFactory object encapsulating the SecretKeyFactorySpi 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 standard name of the requested secret-key algorithm. See Appendix A in the Java Cryptography Architecture Reference Guide Java Cryptography Extension Reference Guide for information about standard algorithm names.
provider - the name of the provider.
Returns:
the new SecretKeyFactory object.
Throws:
NoSuchAlgorithmException - if a SecretKeyFactorySpi implementation for the specified algorithm is not available from the specified provider.
NullPointerException - if the specified algorithm is null.
NoSuchProviderException - if the specified provider is not registered in the security provider list.
IllegalArgumentException - if the provider is null or empty.
See Also:
Provider

getInstance


public static final SecretKeyFactory getInstance(String algorithm,
                                                 Provider provider)
                                          throws NoSuchAlgorithmException
Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.

A new SecretKeyFactory object encapsulating the SecretKeyFactorySpi 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 standard name of the requested secret-key algorithm. See Appendix A in the Java Cryptography Architecture Reference Guide Java Cryptography Extension Reference Guide for information about standard algorithm names.
provider - the provider.
Returns:
the new SecretKeyFactory object.
Throws:
NullPointerException - if the specified algorithm is null.
NoSuchAlgorithmException - if a SecretKeyFactorySpi implementation for the specified algorithm is not available from the specified Provider object.
IllegalArgumentException - if the provider is null.
See Also:
Provider

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.