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344 lines
13 KiB
344 lines
13 KiB
/*
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* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*/
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package java.security;
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import java.security.spec.AlgorithmParameterSpec;
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/**
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* The {@code AlgorithmParameterGenerator} class is used to generate a
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* set of
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* parameters to be used with a certain algorithm. Parameter generators
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* are constructed using the {@code getInstance} factory methods
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* (static methods that return instances of a given class).
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*
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* <P>The object that will generate the parameters can be initialized
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* in two different ways: in an algorithm-independent manner, or in an
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* algorithm-specific manner:
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*
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* <ul>
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* <li>The algorithm-independent approach uses the fact that all parameter
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* generators share the concept of a "size" and a
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* source of randomness. The measure of size is universally shared
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* by all algorithm parameters, though it is interpreted differently
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* for different algorithms. For example, in the case of parameters for
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* the <i>DSA</i> algorithm, "size" corresponds to the size
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* of the prime modulus (in bits).
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* When using this approach, algorithm-specific parameter generation
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* values - if any - default to some standard values, unless they can be
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* derived from the specified size.
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*
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* <li>The other approach initializes a parameter generator object
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* using algorithm-specific semantics, which are represented by a set of
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* algorithm-specific parameter generation values. To generate
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* Diffie-Hellman system parameters, for example, the parameter generation
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* values usually
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* consist of the size of the prime modulus and the size of the
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* random exponent, both specified in number of bits.
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* </ul>
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*
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* <P>In case the client does not explicitly initialize the
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* AlgorithmParameterGenerator
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* (via a call to an {@code init} method), each provider must supply (and
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* document) a default initialization. For example, the Sun provider uses a
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* default modulus prime size of 1024 bits for the generation of DSA
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* parameters.
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*
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* <p> Every implementation of the Java platform is required to support the
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* following standard {@code AlgorithmParameterGenerator} algorithms and
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* keysizes in parentheses:
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* <ul>
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* <li>{@code DiffieHellman} (1024)</li>
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* <li>{@code DSA} (1024)</li>
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* </ul>
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* These algorithms are described in the <a href=
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* "{@docRoot}/../technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
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* AlgorithmParameterGenerator section</a> of the
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* Java Cryptography Architecture Standard Algorithm Name Documentation.
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* Consult the release documentation for your implementation to see if any
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* other algorithms are supported.
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*
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* @author Jan Luehe
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*
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*
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* @see AlgorithmParameters
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* @see java.security.spec.AlgorithmParameterSpec
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*
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* @since 1.2
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*/
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public class AlgorithmParameterGenerator {
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// The provider
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private Provider provider;
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// The provider implementation (delegate)
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private AlgorithmParameterGeneratorSpi paramGenSpi;
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// The algorithm
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private String algorithm;
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/**
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* Creates an AlgorithmParameterGenerator object.
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*
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* @param paramGenSpi the delegate
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* @param provider the provider
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* @param algorithm the algorithm
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*/
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protected AlgorithmParameterGenerator
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(AlgorithmParameterGeneratorSpi paramGenSpi, Provider provider,
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String algorithm) {
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this.paramGenSpi = paramGenSpi;
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this.provider = provider;
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this.algorithm = algorithm;
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}
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/**
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* Returns the standard name of the algorithm this parameter
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* generator is associated with.
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*
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* @return the string name of the algorithm.
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*/
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public final String getAlgorithm() {
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return this.algorithm;
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}
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/**
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* Returns an AlgorithmParameterGenerator object for generating
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* a set of parameters to be used with the specified algorithm.
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*
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* <p> This method traverses the list of registered security Providers,
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* starting with the most preferred Provider.
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* A new AlgorithmParameterGenerator object encapsulating the
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* AlgorithmParameterGeneratorSpi implementation from the first
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* Provider that supports the specified algorithm is returned.
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*
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* <p> Note that the list of registered providers may be retrieved via
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* the {@link Security#getProviders() Security.getProviders()} method.
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*
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* @param algorithm the name of the algorithm this
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* parameter generator is associated with.
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* See the AlgorithmParameterGenerator section in the <a href=
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* "{@docRoot}/../technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
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* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
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* for information about standard algorithm names.
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*
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* @return the new AlgorithmParameterGenerator object.
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*
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* @exception NoSuchAlgorithmException if no Provider supports an
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* AlgorithmParameterGeneratorSpi implementation for the
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* specified algorithm.
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*
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* @see Provider
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*/
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public static AlgorithmParameterGenerator getInstance(String algorithm)
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throws NoSuchAlgorithmException {
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try {
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Object[] objs = Security.getImpl(algorithm,
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"AlgorithmParameterGenerator",
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(String)null);
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return new AlgorithmParameterGenerator
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((AlgorithmParameterGeneratorSpi)objs[0],
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(Provider)objs[1],
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algorithm);
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} catch(NoSuchProviderException e) {
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throw new NoSuchAlgorithmException(algorithm + " not found");
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}
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}
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/**
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* Returns an AlgorithmParameterGenerator object for generating
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* a set of parameters to be used with the specified algorithm.
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*
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* <p> A new AlgorithmParameterGenerator object encapsulating the
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* AlgorithmParameterGeneratorSpi implementation from the specified provider
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* is returned. The specified provider must be registered
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* in the security provider list.
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*
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* <p> Note that the list of registered providers may be retrieved via
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* the {@link Security#getProviders() Security.getProviders()} method.
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*
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* @param algorithm the name of the algorithm this
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* parameter generator is associated with.
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* See the AlgorithmParameterGenerator section in the <a href=
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* "{@docRoot}/../technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
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* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
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* for information about standard algorithm names.
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*
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* @param provider the string name of the Provider.
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*
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* @return the new AlgorithmParameterGenerator object.
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*
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* @exception NoSuchAlgorithmException if an AlgorithmParameterGeneratorSpi
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* implementation for the specified algorithm is not
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* available from the specified provider.
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*
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* @exception NoSuchProviderException if the specified provider is not
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* registered in the security provider list.
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*
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* @exception IllegalArgumentException if the provider name is null
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* or empty.
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*
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* @see Provider
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*/
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public static AlgorithmParameterGenerator getInstance(String algorithm,
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String provider)
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throws NoSuchAlgorithmException, NoSuchProviderException
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{
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if (provider == null || provider.length() == 0)
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throw new IllegalArgumentException("missing provider");
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Object[] objs = Security.getImpl(algorithm,
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"AlgorithmParameterGenerator",
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provider);
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return new AlgorithmParameterGenerator
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((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
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algorithm);
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}
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/**
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* Returns an AlgorithmParameterGenerator object for generating
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* a set of parameters to be used with the specified algorithm.
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*
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* <p> A new AlgorithmParameterGenerator object encapsulating the
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* AlgorithmParameterGeneratorSpi implementation from the specified Provider
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* object is returned. Note that the specified Provider object
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* does not have to be registered in the provider list.
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*
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* @param algorithm the string name of the algorithm this
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* parameter generator is associated with.
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* See the AlgorithmParameterGenerator section in the <a href=
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* "{@docRoot}/../technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
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* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
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* for information about standard algorithm names.
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*
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* @param provider the Provider object.
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*
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* @return the new AlgorithmParameterGenerator object.
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*
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* @exception NoSuchAlgorithmException if an AlgorithmParameterGeneratorSpi
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* implementation for the specified algorithm is not available
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* from the specified Provider object.
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*
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* @exception IllegalArgumentException if the specified provider is null.
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*
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* @see Provider
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*
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* @since 1.4
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*/
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public static AlgorithmParameterGenerator getInstance(String algorithm,
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Provider provider)
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throws NoSuchAlgorithmException
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{
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if (provider == null)
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throw new IllegalArgumentException("missing provider");
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Object[] objs = Security.getImpl(algorithm,
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"AlgorithmParameterGenerator",
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provider);
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return new AlgorithmParameterGenerator
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((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
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algorithm);
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}
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/**
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* Returns the provider of this algorithm parameter generator object.
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*
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* @return the provider of this algorithm parameter generator object
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*/
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public final Provider getProvider() {
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return this.provider;
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}
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/**
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* Initializes this parameter generator for a certain size.
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* To create the parameters, the {@code SecureRandom}
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* implementation of the highest-priority installed provider is used as
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* the source of randomness.
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* (If none of the installed providers supply an implementation of
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* {@code SecureRandom}, a system-provided source of randomness is
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* used.)
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*
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* @param size the size (number of bits).
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*/
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public final void init(int size) {
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paramGenSpi.engineInit(size, new SecureRandom());
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}
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/**
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* Initializes this parameter generator for a certain size and source
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* of randomness.
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*
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* @param size the size (number of bits).
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* @param random the source of randomness.
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*/
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public final void init(int size, SecureRandom random) {
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paramGenSpi.engineInit(size, random);
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}
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/**
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* Initializes this parameter generator with a set of algorithm-specific
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* parameter generation values.
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* To generate the parameters, the {@code SecureRandom}
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* implementation of the highest-priority installed provider is used as
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* the source of randomness.
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* (If none of the installed providers supply an implementation of
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* {@code SecureRandom}, a system-provided source of randomness is
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* used.)
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*
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* @param genParamSpec the set of algorithm-specific parameter generation values.
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*
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* @exception InvalidAlgorithmParameterException if the given parameter
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* generation values are inappropriate for this parameter generator.
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*/
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public final void init(AlgorithmParameterSpec genParamSpec)
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throws InvalidAlgorithmParameterException {
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paramGenSpi.engineInit(genParamSpec, new SecureRandom());
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}
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/**
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* Initializes this parameter generator with a set of algorithm-specific
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* parameter generation values.
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*
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* @param genParamSpec the set of algorithm-specific parameter generation values.
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* @param random the source of randomness.
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*
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* @exception InvalidAlgorithmParameterException if the given parameter
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* generation values are inappropriate for this parameter generator.
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*/
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public final void init(AlgorithmParameterSpec genParamSpec,
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SecureRandom random)
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throws InvalidAlgorithmParameterException {
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paramGenSpi.engineInit(genParamSpec, random);
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}
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/**
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* Generates the parameters.
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*
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* @return the new AlgorithmParameters object.
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*/
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public final AlgorithmParameters generateParameters() {
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return paramGenSpi.engineGenerateParameters();
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}
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}
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