AlgorithmParameterGenerator

public class AlgorithmParameterGenerator extends Object

The AlgorithmParameterGenerator class is used to generate a set of parameters to be used with a certain algorithm. Parameter generators are constructed using the getInstance factory methods (static methods that return instances of a given class).

The object that will generate the parameters can be initialized in two different ways: in an algorithm-independent manner, or in an algorithm-specific manner:

• The algorithm-independent approach uses the fact that all parameter generators share the concept of a "size" and a source of randomness. The measure of size is universally shared by all algorithm parameters, though it is interpreted differently for different algorithms. For example, in the case of parameters for the DSA algorithm, "size" corresponds to the size of the prime modulus (in bits). When using this approach, algorithm-specific parameter generation values - if any - default to some standard values, unless they can be derived from the specified size.
• The other approach initializes a parameter generator object using algorithm-specific semantics, which are represented by a set of algorithm-specific parameter generation values. To generate Diffie-Hellman system parameters, for example, the parameter generation values usually consist of the size of the prime modulus and the size of the random exponent, both specified in number of bits.

In case the client does not explicitly initialize the AlgorithmParameterGenerator (via a call to an init method), each provider must supply (and document) a default initialization. For example, the Sun provider uses a default modulus prime size of 1024 bits for the generation of DSA parameters.

Android provides the following AlgorithmParameterGenerator algorithms:

Algorithm	Supported API Levels
AES	1-8
DES	1-8
DESede	1-8
DH	1+
DSA	1+

These algorithms are described in the AlgorithmParameterGenerator section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

See Also

• AlgorithmParameters
• AlgorithmParameterSpec

Protected Constructor Summary

AlgorithmParameterGenerator(AlgorithmParameterGeneratorSpi paramGenSpi, Provider provider, String algorithm) Creates an AlgorithmParameterGenerator object.

Public Method Summary

final AlgorithmParameters	generateParameters() Generates the parameters.
final String	getAlgorithm() Returns the standard name of the algorithm this parameter generator is associated with.
static AlgorithmParameterGenerator	getInstance(String algorithm) Returns an AlgorithmParameterGenerator object for generating a set of parameters to be used with the specified algorithm.
static AlgorithmParameterGenerator	getInstance(String algorithm, String provider) Returns an AlgorithmParameterGenerator object for generating a set of parameters to be used with the specified algorithm.
static AlgorithmParameterGenerator	getInstance(String algorithm, Provider provider) Returns an AlgorithmParameterGenerator object for generating a set of parameters to be used with the specified algorithm.
final Provider	getProvider() Returns the provider of this algorithm parameter generator object.
final void	init(AlgorithmParameterSpec genParamSpec, SecureRandom random) Initializes this parameter generator with a set of algorithm-specific parameter generation values.
final void	init(int size) Initializes this parameter generator for a certain size.
final void	init(int size, SecureRandom random) Initializes this parameter generator for a certain size and source of randomness.
final void	init(AlgorithmParameterSpec genParamSpec) Initializes this parameter generator with a set of algorithm-specific parameter generation values.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Protected Constructors

protected AlgorithmParameterGenerator (AlgorithmParameterGeneratorSpi paramGenSpi, Provider provider, String algorithm)

Creates an AlgorithmParameterGenerator object.

Parameters

paramGenSpi	the delegate
provider	the provider
algorithm	the algorithm

Public Methods

public final AlgorithmParameters generateParameters ()

Generates the parameters.

Returns

• the new AlgorithmParameters object.

public final String getAlgorithm ()

Returns the standard name of the algorithm this parameter generator is associated with.

Returns

• the string name of the algorithm.

public static AlgorithmParameterGenerator getInstance (String algorithm)

Returns an AlgorithmParameterGenerator object for generating a set of parameters to be used with the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new AlgorithmParameterGenerator object encapsulating the AlgorithmParameterGeneratorSpi 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 algorithm this parameter generator is associated with. See the AlgorithmParameterGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Returns

• the new AlgorithmParameterGenerator object.

Throws

NoSuchAlgorithmException	if no Provider supports an AlgorithmParameterGeneratorSpi implementation for the specified algorithm.

See Also

• Provider

public static AlgorithmParameterGenerator getInstance (String algorithm, String provider)

Returns an AlgorithmParameterGenerator object for generating a set of parameters to be used with the specified algorithm.

A new AlgorithmParameterGenerator object encapsulating the AlgorithmParameterGeneratorSpi 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 algorithm this parameter generator is associated with. See the AlgorithmParameterGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider	the string name of the Provider.

Returns

• the new AlgorithmParameterGenerator object.

Throws

NoSuchAlgorithmException	if an AlgorithmParameterGeneratorSpi 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.
IllegalArgumentException	if the provider name is null or empty.

See Also

• Provider

public static AlgorithmParameterGenerator getInstance (String algorithm, Provider provider)

Returns an AlgorithmParameterGenerator object for generating a set of parameters to be used with the specified algorithm.

A new AlgorithmParameterGenerator object encapsulating the AlgorithmParameterGeneratorSpi 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 string name of the algorithm this parameter generator is associated with. See the AlgorithmParameterGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider	the Provider object.

Returns

• the new AlgorithmParameterGenerator object.

Throws

NoSuchAlgorithmException	if an AlgorithmParameterGeneratorSpi implementation for the specified algorithm is not available from the specified Provider object.
IllegalArgumentException	if the specified provider is null.

See Also

• Provider

public final Provider getProvider ()

Returns the provider of this algorithm parameter generator object.

Returns

• the provider of this algorithm parameter generator object

public final void init (AlgorithmParameterSpec genParamSpec, SecureRandom random)

Initializes this parameter generator with a set of algorithm-specific parameter generation values.

Parameters

genParamSpec	the set of algorithm-specific parameter generation values.
random	the source of randomness.

Throws

InvalidAlgorithmParameterException	if the given parameter generation values are inappropriate for this parameter generator.

public final void init (int size)

Initializes this parameter generator for a certain size. To create the parameters, the SecureRandom implementation of the highest-priority installed provider is used as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness is used.)

Parameters

size	the size (number of bits).

public final void init (int size, SecureRandom random)

Initializes this parameter generator for a certain size and source of randomness.

Parameters

size	the size (number of bits).
random	the source of randomness.

public final void init (AlgorithmParameterSpec genParamSpec)

Initializes this parameter generator with a set of algorithm-specific parameter generation values. To generate the parameters, the SecureRandom implementation of the highest-priority installed provider is used as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness is used.)

Parameters

genParamSpec	the set of algorithm-specific parameter generation values.

Throws

InvalidAlgorithmParameterException	if the given parameter generation values are inappropriate for this parameter generator.