/*
* @(#)AlgorithmParameterGenerator.java 1.43 06/04/21
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.security;
import java.security.spec.AlgorithmParameterSpec;
/**
* The <code>AlgorithmParameterGenerator</code> class is used to generate a
* set of
* parameters to be used with a certain algorithm. Parameter generators
* are constructed using the <code>getInstance</code> factory methods
* (static methods that return instances of a given class).
*
* <P>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:
*
* <ul>
* <li>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 <i>DSA</i> 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.<P>
*
* <li>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.
* </ul>
*
* <P>In case the client does not explicitly initialize the
* AlgorithmParameterGenerator
* (via a call to an <code>init</code> 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.
*
* @author Jan Luehe
*
* @version 1.43, 04/21/06
*
* @see AlgorithmParameters
* @see java.security.spec.AlgorithmParameterSpec
*
* @since 1.2
*/
public class AlgorithmParameterGenerator {
// The provider
private Provider provider;
// The provider implementation (delegate)
private AlgorithmParameterGeneratorSpi paramGenSpi;
// The algorithm
private String algorithm;
/**
* Creates an AlgorithmParameterGenerator object.
*
* @param paramGenSpi the delegate
* @param provider the provider
* @param algorithm the algorithm
*/
protected AlgorithmParameterGenerator
(AlgorithmParameterGeneratorSpi paramGenSpi, Provider provider,
String algorithm) {
this.paramGenSpi = paramGenSpi;
this.provider = provider;
this.algorithm = algorithm;
}
/**
* Returns the standard name of the algorithm this parameter
* generator is associated with.
*
* @return the string name of the algorithm.
*/
public final String getAlgorithm() {
return this.algorithm;
}
/**
* Returns an AlgorithmParameterGenerator object for generating
* a set of parameters to be used with the specified algorithm.
*
* <p> 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.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the name of the algorithm this
* parameter generator is associated with.
* See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard algorithm names.
*
* @return the new AlgorithmParameterGenerator object.
*
* @exception NoSuchAlgorithmException if no Provider supports an
* AlgorithmParameterGeneratorSpi implementation for the
* specified algorithm.
*
* @see Provider
*/
public static AlgorithmParameterGenerator getInstance(String algorithm)
throws NoSuchAlgorithmException {
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");
}
}
/**
* Returns an AlgorithmParameterGenerator object for generating
* a set of parameters to be used with the specified algorithm.
*
* <p> 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.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the name of the algorithm this
* parameter generator is associated with.
* See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard algorithm names.
*
* @param provider the string name of the Provider.
*
* @return the new AlgorithmParameterGenerator object.
*
* @exception NoSuchAlgorithmException if an AlgorithmParameterGeneratorSpi
* implementation for the specified algorithm is not
* available from the specified provider.
*
* @exception NoSuchProviderException if the specified provider is not
* registered in the security provider list.
*
* @exception IllegalArgumentException if the provider name is null
* or empty.
*
* @see Provider
*/
public static AlgorithmParameterGenerator getInstance(String algorithm,
String provider)
throws NoSuchAlgorithmException, NoSuchProviderException
{
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);
}
/**
* Returns an AlgorithmParameterGenerator object for generating
* a set of parameters to be used with the specified algorithm.
*
* <p> 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.
*
* @param algorithm the string name of the algorithm this
* parameter generator is associated with.
* See Appendix A in the <a href=
* "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
* Java Cryptography Architecture API Specification & Reference </a>
* for information about standard algorithm names.
*
* @param provider the Provider object.
*
* @return the new AlgorithmParameterGenerator object.
*
* @exception NoSuchAlgorithmException if an AlgorithmParameterGeneratorSpi
* implementation for the specified algorithm is not available
* from the specified Provider object.
*
* @exception IllegalArgumentException if the specified provider is null.
*
* @see Provider
*
* @since 1.4
*/
public static AlgorithmParameterGenerator getInstance(String algorithm,
Provider provider)
throws NoSuchAlgorithmException
{
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);
}
/**
* Returns the provider of this algorithm parameter generator object.
*
* @return the provider of this algorithm parameter generator object
*/
public final Provider getProvider() {
return this.provider;
}
/**
* Initializes this parameter generator for a certain size.
* To create the parameters, the <code>SecureRandom</code>
* implementation of the highest-priority installed provider is used as
* the source of randomness.
* (If none of the installed providers supply an implementation of
* <code>SecureRandom</code>, a system-provided source of randomness is
* used.)
*
* @param size the size (number of bits).
*/
public final void init(int size) {
paramGenSpi.engineInit(size, new SecureRandom());
}
/**
* Initializes this parameter generator for a certain size and source
* of randomness.
*
* @param size the size (number of bits).
* @param random the source of randomness.
*/
public final void init(int size, SecureRandom random) {
paramGenSpi.engineInit(size, random);
}
/**
* Initializes this parameter generator with a set of algorithm-specific
* parameter generation values.
* To generate the parameters, the <code>SecureRandom</code>
* implementation of the highest-priority installed provider is used as
* the source of randomness.
* (If none of the installed providers supply an implementation of
* <code>SecureRandom</code>, a system-provided source of randomness is
* used.)
*
* @param genParamSpec the set of algorithm-specific parameter generation values.
*
* @exception InvalidAlgorithmParameterException if the given parameter
* generation values are inappropriate for this parameter generator.
*/
public final void init(AlgorithmParameterSpec genParamSpec)
throws InvalidAlgorithmParameterException {
paramGenSpi.engineInit(genParamSpec, new SecureRandom());
}
/**
* Initializes this parameter generator with a set of algorithm-specific
* parameter generation values.
*
* @param genParamSpec the set of algorithm-specific parameter generation values.
* @param random the source of randomness.
*
* @exception InvalidAlgorithmParameterException if the given parameter
* generation values are inappropriate for this parameter generator.
*/
public final void init(AlgorithmParameterSpec genParamSpec,
SecureRandom random)
throws InvalidAlgorithmParameterException {
paramGenSpi.engineInit(genParamSpec, random);
}
/**
* Generates the parameters.
*
* @return the new AlgorithmParameters object.
*/
public final AlgorithmParameters generateParameters() {
return paramGenSpi.engineGenerateParameters();
}
}
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