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25
26package java.security;
27
28import java.security.spec.AlgorithmParameterSpec;
29
30/**
31 * The {@code AlgorithmParameterGenerator} class is used to generate a
32 * set of
33 * parameters to be used with a certain algorithm. Parameter generators
34 * are constructed using the {@code getInstance} factory methods
35 * (static methods that return instances of a given class).
36 *
37 * <P>The object that will generate the parameters can be initialized
38 * in two different ways: in an algorithm-independent manner, or in an
39 * algorithm-specific manner:
40 *
41 * <ul>
42 * <li>The algorithm-independent approach uses the fact that all parameter
43 * generators share the concept of a "size" and a
44 * source of randomness. The measure of size is universally shared
45 * by all algorithm parameters, though it is interpreted differently
46 * for different algorithms. For example, in the case of parameters for
47 * the <i>DSA</i> algorithm, "size" corresponds to the size
48 * of the prime modulus (in bits).
49 * When using this approach, algorithm-specific parameter generation
50 * values - if any - default to some standard values, unless they can be
51 * derived from the specified size.
52 *
53 * <li>The other approach initializes a parameter generator object
54 * using algorithm-specific semantics, which are represented by a set of
55 * algorithm-specific parameter generation values. To generate
56 * Diffie-Hellman system parameters, for example, the parameter generation
57 * values usually
58 * consist of the size of the prime modulus and the size of the
59 * random exponent, both specified in number of bits.
60 * </ul>
61 *
62 * <P>In case the client does not explicitly initialize the
63 * AlgorithmParameterGenerator
64 * (via a call to an {@code init} method), each provider must supply (and
65 * document) a default initialization. For example, the Sun provider uses a
66 * default modulus prime size of 1024 bits for the generation of DSA
67 * parameters.
68 *
69 * <p> Android provides the following <code>AlgorithmParameterGenerator</code> algorithms:
70 * <table>
71 *   <thead>
72 *     <tr>
73 *       <th>Algorithm</th>
74 *       <th>Supported API Levels</th>
75 *     </tr>
76 *   </thead>
77 *   <tbody>
78 *     <tr class="deprecated">
79 *       <td>AES</td>
80 *       <td>1-8</td>
81 *     </tr>
82 *     <tr class="deprecated">
83 *       <td>DES</td>
84 *       <td>1-8</td>
85 *     </tr>
86 *     <tr class="deprecated">
87 *       <td>DESede</td>
88 *       <td>1-8</td>
89 *     </tr>
90 *     <tr>
91 *       <td>DH</td>
92 *       <td>1+</td>
93 *     </tr>
94 *     <tr>
95 *       <td>DSA</td>
96 *       <td>1+</td>
97 *     </tr>
98 *   </tbody>
99 * </table>
100 *
101 * These algorithms are described in the <a href=
102 * "{@docRoot}openjdk-redirect.html?v=8&path=/technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
103 * AlgorithmParameterGenerator section</a> of the
104 * Java Cryptography Architecture Standard Algorithm Name Documentation.
105 *
106 * @author Jan Luehe
107 *
108 *
109 * @see AlgorithmParameters
110 * @see java.security.spec.AlgorithmParameterSpec
111 *
112 * @since 1.2
113 */
114
115public class AlgorithmParameterGenerator {
116
117    // The provider
118    private Provider provider;
119
120    // The provider implementation (delegate)
121    private AlgorithmParameterGeneratorSpi paramGenSpi;
122
123    // The algorithm
124    private String algorithm;
125
126    /**
127     * Creates an AlgorithmParameterGenerator object.
128     *
129     * @param paramGenSpi the delegate
130     * @param provider the provider
131     * @param algorithm the algorithm
132     */
133    protected AlgorithmParameterGenerator
134    (AlgorithmParameterGeneratorSpi paramGenSpi, Provider provider,
135     String algorithm) {
136        this.paramGenSpi = paramGenSpi;
137        this.provider = provider;
138        this.algorithm = algorithm;
139    }
140
141    /**
142     * Returns the standard name of the algorithm this parameter
143     * generator is associated with.
144     *
145     * @return the string name of the algorithm.
146     */
147    public final String getAlgorithm() {
148        return this.algorithm;
149    }
150
151    /**
152     * Returns an AlgorithmParameterGenerator object for generating
153     * a set of parameters to be used with the specified algorithm.
154     *
155     * <p> This method traverses the list of registered security Providers,
156     * starting with the most preferred Provider.
157     * A new AlgorithmParameterGenerator object encapsulating the
158     * AlgorithmParameterGeneratorSpi implementation from the first
159     * Provider that supports the specified algorithm is returned.
160     *
161     * <p> Note that the list of registered providers may be retrieved via
162     * the {@link Security#getProviders() Security.getProviders()} method.
163     *
164     * @param algorithm the name of the algorithm this
165     * parameter generator is associated with.
166     * See the AlgorithmParameterGenerator section in the <a href=
167     * "{@docRoot}openjdk-redirect.html?v=8&path=/technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
168     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
169     * for information about standard algorithm names.
170     *
171     * @return the new AlgorithmParameterGenerator object.
172     *
173     * @exception NoSuchAlgorithmException if no Provider supports an
174     *          AlgorithmParameterGeneratorSpi implementation for the
175     *          specified algorithm.
176     *
177     * @see Provider
178     */
179    public static AlgorithmParameterGenerator getInstance(String algorithm)
180        throws NoSuchAlgorithmException {
181            try {
182                Object[] objs = Security.getImpl(algorithm,
183                                                 "AlgorithmParameterGenerator",
184                                                 (String)null);
185                return new AlgorithmParameterGenerator
186                    ((AlgorithmParameterGeneratorSpi)objs[0],
187                     (Provider)objs[1],
188                     algorithm);
189            } catch(NoSuchProviderException e) {
190                throw new NoSuchAlgorithmException(algorithm + " not found");
191            }
192    }
193
194    /**
195     * Returns an AlgorithmParameterGenerator object for generating
196     * a set of parameters to be used with the specified algorithm.
197     *
198     * <p> A new AlgorithmParameterGenerator object encapsulating the
199     * AlgorithmParameterGeneratorSpi implementation from the specified provider
200     * is returned.  The specified provider must be registered
201     * in the security provider list.
202     *
203     * <p> Note that the list of registered providers may be retrieved via
204     * the {@link Security#getProviders() Security.getProviders()} method.
205     *
206     * @param algorithm the name of the algorithm this
207     * parameter generator is associated with.
208     * See the AlgorithmParameterGenerator section in the <a href=
209     * "{@docRoot}openjdk-redirect.html?v=8&path=/technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
210     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
211     * for information about standard algorithm names.
212     *
213     * @param provider the string name of the Provider.
214     *
215     * @return the new AlgorithmParameterGenerator object.
216     *
217     * @exception NoSuchAlgorithmException if an AlgorithmParameterGeneratorSpi
218     *          implementation for the specified algorithm is not
219     *          available from the specified provider.
220     *
221     * @exception NoSuchProviderException if the specified provider is not
222     *          registered in the security provider list.
223     *
224     * @exception IllegalArgumentException if the provider name is null
225     *          or empty.
226     *
227     * @see Provider
228     */
229    public static AlgorithmParameterGenerator getInstance(String algorithm,
230                                                          String provider)
231        throws NoSuchAlgorithmException, NoSuchProviderException
232    {
233        if (provider == null || provider.length() == 0)
234            throw new IllegalArgumentException("missing provider");
235        Object[] objs = Security.getImpl(algorithm,
236                                         "AlgorithmParameterGenerator",
237                                         provider);
238        return new AlgorithmParameterGenerator
239            ((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
240             algorithm);
241    }
242
243    /**
244     * Returns an AlgorithmParameterGenerator object for generating
245     * a set of parameters to be used with the specified algorithm.
246     *
247     * <p> A new AlgorithmParameterGenerator object encapsulating the
248     * AlgorithmParameterGeneratorSpi implementation from the specified Provider
249     * object is returned.  Note that the specified Provider object
250     * does not have to be registered in the provider list.
251     *
252     * @param algorithm the string name of the algorithm this
253     * parameter generator is associated with.
254     * See the AlgorithmParameterGenerator section in the <a href=
255     * "{@docRoot}openjdk-redirect.html?v=8&path=/technotes/guides/security/StandardNames.html#AlgorithmParameterGenerator">
256     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
257     * for information about standard algorithm names.
258     *
259     * @param provider the Provider object.
260     *
261     * @return the new AlgorithmParameterGenerator object.
262     *
263     * @exception NoSuchAlgorithmException if an AlgorithmParameterGeneratorSpi
264     *          implementation for the specified algorithm is not available
265     *          from the specified Provider object.
266     *
267     * @exception IllegalArgumentException if the specified provider is null.
268     *
269     * @see Provider
270     *
271     * @since 1.4
272     */
273    public static AlgorithmParameterGenerator getInstance(String algorithm,
274                                                          Provider provider)
275        throws NoSuchAlgorithmException
276    {
277        if (provider == null)
278            throw new IllegalArgumentException("missing provider");
279        Object[] objs = Security.getImpl(algorithm,
280                                         "AlgorithmParameterGenerator",
281                                         provider);
282        return new AlgorithmParameterGenerator
283            ((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
284             algorithm);
285    }
286
287    /**
288     * Returns the provider of this algorithm parameter generator object.
289     *
290     * @return the provider of this algorithm parameter generator object
291     */
292    public final Provider getProvider() {
293        return this.provider;
294    }
295
296    /**
297     * Initializes this parameter generator for a certain size.
298     * To create the parameters, the {@code SecureRandom}
299     * implementation of the highest-priority installed provider is used as
300     * the source of randomness.
301     * (If none of the installed providers supply an implementation of
302     * {@code SecureRandom}, a system-provided source of randomness is
303     * used.)
304     *
305     * @param size the size (number of bits).
306     */
307    public final void init(int size) {
308        paramGenSpi.engineInit(size, new SecureRandom());
309    }
310
311    /**
312     * Initializes this parameter generator for a certain size and source
313     * of randomness.
314     *
315     * @param size the size (number of bits).
316     * @param random the source of randomness.
317     */
318    public final void init(int size, SecureRandom random) {
319        paramGenSpi.engineInit(size, random);
320    }
321
322    /**
323     * Initializes this parameter generator with a set of algorithm-specific
324     * parameter generation values.
325     * To generate the parameters, the {@code SecureRandom}
326     * implementation of the highest-priority installed provider is used as
327     * the source of randomness.
328     * (If none of the installed providers supply an implementation of
329     * {@code SecureRandom}, a system-provided source of randomness is
330     * used.)
331     *
332     * @param genParamSpec the set of algorithm-specific parameter generation values.
333     *
334     * @exception InvalidAlgorithmParameterException if the given parameter
335     * generation values are inappropriate for this parameter generator.
336     */
337    public final void init(AlgorithmParameterSpec genParamSpec)
338        throws InvalidAlgorithmParameterException {
339            paramGenSpi.engineInit(genParamSpec, new SecureRandom());
340    }
341
342    /**
343     * Initializes this parameter generator with a set of algorithm-specific
344     * parameter generation values.
345     *
346     * @param genParamSpec the set of algorithm-specific parameter generation values.
347     * @param random the source of randomness.
348     *
349     * @exception InvalidAlgorithmParameterException if the given parameter
350     * generation values are inappropriate for this parameter generator.
351     */
352    public final void init(AlgorithmParameterSpec genParamSpec,
353                           SecureRandom random)
354        throws InvalidAlgorithmParameterException {
355            paramGenSpi.engineInit(genParamSpec, random);
356    }
357
358    /**
359     * Generates the parameters.
360     *
361     * @return the new AlgorithmParameters object.
362     */
363    public final AlgorithmParameters generateParameters() {
364        return paramGenSpi.engineGenerateParameters();
365    }
366}
367