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:

Name 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.

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

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

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 implementa