libjava/java/security/KeyPairGenerator.java

   1 /* KeyPairGenerator.java --- Key Pair Generator Class
   2    Copyright (C) 1999, 2002, 2003 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.security;
  39
  40 import java.security.spec.AlgorithmParameterSpec;
  41
  42 import gnu.java.security.Engine;
  43
  44 /**
  45  * <p>The <code>KeyPairGenerator</code> class is used to generate pairs of
  46  * public and private keys. Key pair generators are constructed using the
  47  * <code>getInstance()</code> factory methods (static methods that return
  48  * instances of a given class).</p>
  49  *
  50  * <p>A Key pair generator for a particular algorithm creates a public/private
  51  * key pair that can be used with this algorithm. It also associates
  52  * algorithm-specific parameters with each of the generated keys.</p>
  53  *
  54  * <p>There are two ways to generate a key pair: in an algorithm-independent
  55  * manner, and in an algorithm-specific manner. The only difference between the
  56  * two is the initialization of the object:</p>
  57  *
  58  * <ul>
  59  *    <li><b>Algorithm-Independent Initialization</b><br/>
  60  *    All key pair generators share the concepts of a <i>keysize</i> and a
  61  *    <i>source of randomness</i>. The <i>keysize</i> is interpreted differently
  62  *    for different algorithms (e.g., in the case of the <i>DSA</i> algorithm,
  63  *    the <i>keysize</i> corresponds to the length of the modulus). There is an
  64  *    <code>initialize()</code> method in this <code>KeyPairGenerator</code>
  65  *    class that takes these two universally shared types of arguments. There
  66  *    is also one that takes just a <i>keysize</i> argument, and uses the
  67  *    {@link SecureRandom} implementation of the highest-priority installed
  68  *    provider as the <i>source of randomness</i>. (If none of the installed
  69  *    providers supply an implementation of {@link SecureRandom}, a
  70  *    system-provided source of randomness is used.)<br/><br/>
  71  *
  72  *    Since no other parameters are specified when you call the above
  73  *    algorithm-independent initialize methods, it is up to the provider what
  74  *    to do about the algorithm-specific parameters (if any) to be associated
  75  *    with each of the keys.<br/><br/>
  76  *
  77  *    If the algorithm is the <i>DSA</i> algorithm, and the <i>keysize</i>
  78  *    (modulus size) is <code>512</code>, <code>768</code>, or <code>1024</code>,
  79  *    then the <b>GNU</b> provider uses a set of precomputed values for the
  80  *    <code>p</code>, <code>q</code>, and <code>g</code> parameters. If the
  81  *    <i>modulus size</i> is not one of the above values, the <b>GNU</b>
  82  *    provider creates a new set of parameters. Other providers might have
  83  *    precomputed parameter sets for more than just the three modulus sizes
  84  *    mentioned above. Still others might not have a list of precomputed
  85  *    parameters at all and instead always create new parameter sets.<br/></li>
  86  *
  87  *    <li><b>Algorithm-Specific Initialization</b><br/>
  88  *    For situations where a set of algorithm-specific parameters already
  89  *    exists (e.g., so-called <i>community parameters</i> in <i>DSA</i>), there
  90  *    are two initialize methods that have an {@link AlgorithmParameterSpec}
  91  *    argument. One also has a {@link SecureRandom} argument, while the the
  92  *    other uses the {@link SecureRandom} implementation of the highest-priority
  93  *    installed provider as the source of randomness. (If none of the installed
  94  *    providers supply an implementation of {@link SecureRandom}, a
  95  *    system-provided source of randomness is used.)</li>
  96  * </ul>
  97  *
  98  * <p>In case the client does not explicitly initialize the
  99  * <code>KeyPairGenerator</code> (via a call to an initialize method), each
 100  * provider must supply (and document) a default initialization. For example,
 101  * the <b>GNU</b> provider uses a default modulus size (keysize) of
 102  * <code>1024</code> bits.</p>
 103  *
 104  * <p>Note that this class is abstract and extends from {@link
 105  * KeyPairGeneratorSpi} for historical reasons. Application developers should
 106  * only take notice of the methods defined in this <code>KeyPairGenerator</code>
 107  * class; all the methods in the superclass are intended for cryptographic
 108  * service providers who wish to supply their own implementations of key pair
 109  * generators.</p>
 110  *
 111  * @see Signature
 112  * @see KeyPair
 113  * @see AlgorithmParameterSpec
 114  * @author Mark Benvenuto
 115  * @author Casey Marshall
 116  */
 117 public abstract class KeyPairGenerator extends KeyPairGeneratorSpi
 118 {
 119   /** The service name for key pair generators. */
 120   private static final String KEY_PAIR_GENERATOR = "KeyPairGenerator";
 121
 122   Provider provider;
 123   private String algorithm;
 124
 125   /**
 126    * Creates a <code>KeyPairGenerator</code> object for the specified
 127    * algorithm.
 128    *
 129    * @param algorithm the standard string name of the algorithm.
 130    * See Appendix A in the Java Cryptography Architecture API
 131    * Specification &amp; Reference for information about standard
 132    * algorithm names.
 133    */
 134   protected KeyPairGenerator(String algorithm)
 135   {
 136     this.algorithm = algorithm;
 137     this.provider = null;
 138   }
 139
 140   /**
 141    * Returns the standard name of the algorithm for this key pair generator.
 142    * See Appendix A in the Java Cryptography Architecture API Specification
 143    * &amp; Reference for information about standard algorithm names.
 144    *
 145    * @return the standard string name of the algorithm.
 146    */
 147   public String getAlgorithm()
 148   {
 149     return algorithm;
 150   }
 151
 152   /**
 153    * Generates a <code>KeyPairGenerator</code> object that implements the
 154    * specified digest algorithm. If the default provider package provides an
 155    * implementation of the requested digest algorithm, an instance of
 156    * <code>KeyPairGenerator</code> containing that implementation is returned.
 157    * If the algorithm is not available in the default package, other packages
 158    * are searched.
 159    *
 160    * @param algorithm the standard string name of the algorithm. See Appendix A
 161    * in the Java Cryptography Architecture API Specification &amp; Reference for
 162    * information about standard algorithm names.
 163    * @return the new <code>KeyPairGenerator</code> object.
 164    * @throws NoSuchAlgorithmException if the algorithm is not available in the
 165    * environment.
 166    */
 167   public static KeyPairGenerator getInstance(String algorithm)
 168     throws NoSuchAlgorithmException
 169   {
 170     Provider[] p = Security.getProviders();
 171     for (int i = 0; i < p.length; i++)
 172       {
 173         try
 174           {
 175             return getInstance(algorithm, p[i]);
 176           }
 177         catch (NoSuchAlgorithmException ignored) {}
 178       }
 179
 180     throw new NoSuchAlgorithmException(algorithm);
 181   }
 182
 183   /**
 184    * Generates a <code>KeyPairGenerator</code> object implementing the
 185    * specified algorithm, as supplied from the specified provider, if
 186    * such an algorithm is available from the provider.
 187    *
 188    * @param algorithm the standard string name of the algorithm. See
 189    * Appendix A in the Java Cryptography Architecture API Specification
 190    * &amp; Reference for information about standard algorithm names.
 191    * @param provider the string name of the provider.
 192    * @return the new <code>KeyPairGenerator</code> object.
 193    * @throws NoSuchAlgorithmException if the algorithm is not available
 194    * from the provider.
 195    * @throws NoSuchProviderException if the provider is not available in the
 196    * environment.
 197    * @throws IllegalArgumentException if the provider name is <code>null</code>
 198    * or empty.
 199    * @see Provider
 200    */
 201   public static KeyPairGenerator getInstance(String algorithm, String provider)
 202     throws NoSuchAlgorithmException, NoSuchProviderException
 203   {
 204     Provider p = Security.getProvider(provider);
 205     if (p == null)
 206       throw new NoSuchProviderException(provider);
 207
 208     return getInstance(algorithm, p);
 209   }
 210
 211   /**
 212    * Generates a <code>KeyPairGenerator</code> object implementing the specified
 213    * algorithm, as supplied from the specified provider, if such an algorithm is
 214    * available from the provider. Note: the provider doesn't have to be
 215    * registered.
 216    *
 217    * @param algorithm the standard string name of the algorithm. See Appendix A
 218    * in the Java Cryptography Architecture API Specification &amp; Reference for
 219    * information about standard algorithm names.
 220    * @param provider the provider.
 221    * @return the new <code>KeyPairGenerator</code> object.
 222    * @throws NoSuchAlgorithmException if the <code>algorithm</code> is not
 223    * available from the <code>provider</code>.
 224    * @throws IllegalArgumentException if the <code>provider</code> is
 225    * <code>null</code>.
 226    * @since 1.4
 227    * @see Provider
 228    */
 229   public static KeyPairGenerator getInstance(String algorithm,
 230                                              Provider provider)
 231     throws NoSuchAlgorithmException
 232   {
 233     if (provider == null)
 234       throw new IllegalArgumentException("Illegal provider");
 235
 236     Object o = null;
 237     try
 238       {
 239         o = Engine.getInstance(KEY_PAIR_GENERATOR, algorithm, provider);
 240       }
 241     catch (java.lang.reflect.InvocationTargetException ite)
 242       {
 243         throw new NoSuchAlgorithmException(algorithm);
 244       }
 245
 246     KeyPairGenerator result = null;
 247     if (o instanceof KeyPairGeneratorSpi)
 248       {
 249         result = new DummyKeyPairGenerator((KeyPairGeneratorSpi) o, algorithm);
 250       }
 251     else if (o instanceof KeyPairGenerator)
 252       {
 253         result = (KeyPairGenerator) o;
 254         result.algorithm = algorithm;
 255       }
 256     result.provider = provider;
 257     return result;
 258   }
 259
 260   /**
 261    * Returns the provider of this key pair generator object.
 262    *
 263    * @return the provider of this key pair generator object.
 264    */
 265   public final Provider getProvider()
 266   {
 267     return provider;
 268   }
 269
 270   /**
 271    * Initializes the key pair generator for a certain keysize using a default
 272    * parameter set and the {@link SecureRandom} implementation of the
 273    * highest-priority installed provider as the source of randomness. (If none
 274    * of the installed providers supply an implementation of {@link SecureRandom},
 275    * a system-provided source of randomness is used.)
 276    *
 277    * @param keysize the keysize. This is an algorithm-specific metric, such as
 278    * modulus length, specified in number of bits.
 279    * @throws InvalidParameterException if the keysize is not supported by this
 280    * <code>KeyPairGenerator</code> object.
 281    */
 282   public void initialize(int keysize)
 283   {
 284     initialize(keysize, new SecureRandom());
 285   }
 286
 287   /**
 288    * Initializes the key pair generator for a certain keysize with the given
 289    * source of randomness (and a default parameter set).
 290    *
 291    * @param keysize the keysize. This is an algorithm-specific metric, such as
 292    * modulus length, specified in number of bits.
 293    * @param random the source of randomness.
 294    * @throws InvalidParameterException if the <code>keysize</code> is not
 295    * supported by this <code>KeyPairGenerator</code> object.
 296    * @since 1.2
 297    */
 298   public void initialize(int keysize, SecureRandom random)
 299   {
 300     initialize(keysize, random);
 301   }
 302
 303   /**
 304    * <p>Initializes the key pair generator using the specified parameter set and
 305    * the {@link SecureRandom} implementation of the highest-priority installed
 306    * provider as the source of randomness. (If none of the installed providers
 307    * supply an implementation of {@link SecureRandom}, a system-provided source
 308    * of randomness is used.)</p>
 309    *
 310    * <p>This concrete method has been added to this previously-defined abstract
 311    * class. This method calls the
 312    * {@link KeyPairGeneratorSpi#initialize(AlgorithmParameterSpec, SecureRandom)}
 313    * initialize method, passing it <code>params</code> and a source of
 314    * randomness (obtained from the highest-priority installed provider or
 315    * system-provided if none of the installed providers supply one). That
 316    * initialize method always throws an {@link UnsupportedOperationException}
 317    * if it is not overridden by the provider.</p>
 318    *
 319    * @param params the parameter set used to generate the keys.
 320    * @throws InvalidAlgorithmParameterException if the given parameters are
 321    * inappropriate for this key pair generator.
 322    * @since 1.2
 323    */
 324   public void initialize(AlgorithmParameterSpec params)
 325     throws InvalidAlgorithmParameterException
 326   {
 327     initialize(params, new SecureRandom());
 328   }
 329
 330   /**
 331    * <p>Initializes the key pair generator with the given parameter set and
 332    * source of randomness.</p>
 333    *
 334    * <p>This concrete method has been added to this previously-defined abstract
 335    * class. This method calls the
 336    * {@link KeyPairGeneratorSpi#initialize(AlgorithmParameterSpec, SecureRandom)}
 337    * initialize method, passing it <code>params</code> and <code>random</code>.
 338    * That initialize method always throws an {@link UnsupportedOperationException}
 339    * if it is not overridden by the provider.</p>
 340    *
 341    * @param params the parameter set used to generate the keys.
 342    * @param random the source of randomness.
 343    * @throws InvalidAlgorithmParameterException if the given parameters are
 344    * inappropriate for this key pair generator.
 345    * @since 1.2
 346    */
 347   public void initialize(AlgorithmParameterSpec params, SecureRandom random)
 348     throws InvalidAlgorithmParameterException
 349   {
 350     super.initialize(params, random);
 351   }
 352
 353   /**
 354    * <p>Generates a key pair.</p>
 355    *
 356    * <p>If this <code>KeyPairGenerator</code> has not been initialized
 357    * explicitly, provider-specific defaults will be used for the size and other
 358    * (algorithm-specific) values of the generated keys.</p>
 359    *
 360    * <p>This will generate a new key pair every time it is called.</p>
 361    *
 362    * <p>This method is functionally equivalent to {@link #generateKeyPair()}.</p>
 363    *
 364    * @return the generated key pair.
 365    * @since 1.2
 366    */
 367   public final KeyPair genKeyPair()
 368   {
 369     try
 370       {
 371         return getInstance("DSA", "GNU").generateKeyPair();
 372       }
 373     catch (Exception e)
 374       {
 375         System.err.println("genKeyPair failed: " + e);
 376         e.printStackTrace();
 377         return null;
 378       }
 379   }
 380
 381   /**
 382    * <p>Generates a key pair.</p>
 383    *
 384    * <p>If this <code>KeyPairGenerator</code> has not been initialized
 385    * explicitly, provider-specific defaults will be used for the size and other
 386    * (algorithm-specific) values of the generated keys.</p>
 387    *
 388    * <p>This will generate a new key pair every time it is called.</p>
 389    *
 390    * <p>This method is functionally equivalent to {@link #genKeyPair()}.</p>
 391    *
 392    * @return the generated key pair.
 393    */
 394   public KeyPair generateKeyPair()
 395   {
 396     return genKeyPair();
 397   }
 398 }