AlgorithmParameterGeneratorpublic 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. |
| Fields Summary |
|---|
| private Provider | provider | | private AlgorithmParameterGeneratorSpi | paramGenSpi | | private String | algorithm |
| Constructors Summary |
|---|
protected AlgorithmParameterGenerator(AlgorithmParameterGeneratorSpi paramGenSpi, Provider provider, String algorithm)Creates an AlgorithmParameterGenerator object.
this.paramGenSpi = paramGenSpi;
this.provider = provider;
this.algorithm = algorithm;
|
| Methods Summary |
|---|
| public final java.security.AlgorithmParameters | generateParameters()Generates the parameters.
return paramGenSpi.engineGenerateParameters();
| | public final java.lang.String | getAlgorithm()Returns the standard name of the algorithm this parameter
generator is associated with.
return this.algorithm;
| | public static java.security.AlgorithmParameterGenerator | getInstance(java.lang.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 {@link Security#getProviders() Security.getProviders()} method.
try {
Object[] objs = Security.getImpl(algorithm,
"AlgorithmParameterGenerator",
(String)null);
return new AlgorithmParameterGenerator
((AlgorithmParameterGeneratorSpi)objs[0],
(Provider)objs[1],
algorithm);
} catch(NoSuchProviderException e) {
throw new NoSuchAlgorithmException(algorithm + " not found");
}
| | public static java.security.AlgorithmParameterGenerator | getInstance(java.lang.String algorithm, java.lang.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 {@link Security#getProviders() Security.getProviders()} method.
if (provider == null || provider.length() == 0)
throw new IllegalArgumentException("missing provider");
Object[] objs = Security.getImpl(algorithm,
"AlgorithmParameterGenerator",
provider);
return new AlgorithmParameterGenerator
((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
algorithm);
| | public static java.security.AlgorithmParameterGenerator | getInstance(java.lang.String algorithm, java.security.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.
if (provider == null)
throw new IllegalArgumentException("missing provider");
Object[] objs = Security.getImpl(algorithm,
"AlgorithmParameterGenerator",
provider);
return new AlgorithmParameterGenerator
((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
algorithm);
| | public final java.security.Provider | getProvider()Returns the provider of this algorithm parameter generator object.
return this.provider;
| | public final void | init(java.security.spec.AlgorithmParameterSpec genParamSpec, java.security.SecureRandom random)Initializes this parameter generator with a set of algorithm-specific
parameter generation values.
paramGenSpi.engineInit(genParamSpec, random);
| | 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.)
paramGenSpi.engineInit(size, new SecureRandom());
| | public final void | init(int size, java.security.SecureRandom random)Initializes this parameter generator for a certain size and source
of randomness.
paramGenSpi.engineInit(size, random);
| | public final void | init(java.security.spec.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.)
paramGenSpi.engineInit(genParamSpec, new SecureRandom());
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