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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

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

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 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 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 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.