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 bidirectional, 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 DESede (Triple DES) secret key factory supplied by the "SunJCE" provider supports DESedeKeySpec as a transparent representation of Triple DES keys.

Every implementation of the Java platform is required to support the following standard SecretKeyFactory algorithms:

• PBEWithHmacSHA256AndAES_128
• PBEWithHmacSHA256AndAES_256
• PBKDF2WithHmacSHA256

These algorithms are described in the SecretKeyFactory section of the Java Security Standard Algorithm Names Specification. Consult the release documentation for your implementation to see if any other algorithms are supported.

Since:

1.4

External Specifications

• Java Security Standard Algorithm Names

See Also:

• SecretKey
• DESedeKeySpec
• PBEKeySpec

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	SecretKeyFactory(SecretKeyFactorySpi keyFacSpi, Provider provider, String algorithm)	Creates a SecretKeyFactory object.

Method Summary

Modifier and Type	Method	Description
final SecretKey	generateSecret(KeySpec keySpec)	Generates a SecretKey object from the provided key specification (key material).
final String	getAlgorithm()	Returns the algorithm name of this SecretKeyFactory object.
static final SecretKeyFactory	getInstance(String algorithm)	Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
static final SecretKeyFactory	getInstance(String algorithm, String provider)	Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
static final SecretKeyFactory	getInstance(String algorithm, Provider provider)	Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
final KeySpec	getKeySpec(SecretKey key, Class<?> keySpec)	Returns a specification (key material) of the given key object in the requested format.
final Provider	getProvider()	Returns the provider of this SecretKeyFactory object.
final 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 declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
String	toString()	Returns a string representation of the object.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details

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 Details

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.

Implementation Note:

The JDK Reference Implementation additionally uses the jdk.security.provider.preferred Security property to determine the preferred provider order for the specified algorithm. This may be different from the order of providers returned by Security.getProviders().

Parameters:

algorithm - the standard name of the requested secret key algorithm. See the SecretKeyFactory section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.

Returns:

the new SecretKeyFactory object

Throws:

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

NullPointerException - if algorithm is null

External Specifications

• Java Security Standard Algorithm Names

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 the SecretKeyFactory section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.

provider - the name of the provider.

Returns:

the new SecretKeyFactory object

Throws:

IllegalArgumentException - if the provider is null or empty

NoSuchAlgorithmException - if a SecretKeyFactorySpi 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

NullPointerException - if algorithm is null

External Specifications

• Java Security Standard Algorithm Names

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 the SecretKeyFactory section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.

provider - the provider.

Returns:

the new SecretKeyFactory object

Throws:

IllegalArgumentException - if the provider is null

NoSuchAlgorithmException - if a SecretKeyFactorySpi implementation for the specified algorithm is not available from the specified Provider object

NullPointerException - if algorithm is null

External Specifications

• Java Security Standard Algorithm Names

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.