Class 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.

Every implementation of the Java platform is required to support the following standard AlgorithmParameterGenerator algorithms and keysizes in parentheses:

• DiffieHellman (1024)
• DSA (1024)

These algorithms are described in the AlgorithmParameterGenerator section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.

Constructors

AlgorithmParameterGenerator

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

Creates an AlgorithmParameterGenerator object.

Parameters:

paramGenSpi - the delegate

provider - the provider

algorithm - the algorithm

Methods

getAlgorithm

public final String getAlgorithm()

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

Returns:

the string name of the algorithm.

getInstance

public static AlgorithmParameterGenerator getInstance(String algorithm)
                                               throws NoSuchAlgorithmException

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

getInstance

public static AlgorithmParameterGenerator getInstance(String algorithm,
                                                      String provider)
                                               throws NoSuchAlgorithmException,
                                                      NoSuchProviderException

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

getInstance

public static AlgorithmParameterGenerator getInstance(String algorithm,
                                                      Provider provider)
                                               throws NoSuchAlgorithmException

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.

Since:

1.4

See Also:

Provider

getProvider

public final Provider getProvider()

Returns the provider of this algorithm parameter generator object.

Returns:

the provider of this algorithm parameter generator object

init

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).

init

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.

init

public final void init(AlgorithmParameterSpec genParamSpec)
                throws InvalidAlgorithmParameterException

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.

init

public final void init(AlgorithmParameterSpec genParamSpec,
                       SecureRandom random)
                throws InvalidAlgorithmParameterException

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.

generateParameters

public final AlgorithmParameters generateParameters()

Generates the parameters.

Returns:

the new AlgorithmParameters object.