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    1   /*
    2    * Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package javax.crypto;
   27   
   28   import java.security;
   29   import java.security.spec;
   30   
   31   /**
   32    * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
   33    * for the <code>KeyAgreement</code> class.
   34    * All the abstract methods in this class must be implemented by each
   35    * cryptographic service provider who wishes to supply the implementation
   36    * of a particular key agreement algorithm.
   37    *
   38    * <p> The keys involved in establishing a shared secret are created by one
   39    * of the
   40    * key generators (<code>KeyPairGenerator</code> or
   41    * <code>KeyGenerator</code>), a <code>KeyFactory</code>, or as a result from
   42    * an intermediate phase of the key agreement protocol
   43    * ({@link #engineDoPhase(java.security.Key, boolean) engineDoPhase}).
   44    *
   45    * <p> For each of the correspondents in the key exchange,
   46    * <code>engineDoPhase</code>
   47    * needs to be called. For example, if the key exchange is with one other
   48    * party, <code>engineDoPhase</code> needs to be called once, with the
   49    * <code>lastPhase</code> flag set to <code>true</code>.
   50    * If the key exchange is
   51    * with two other parties, <code>engineDoPhase</code> needs to be called twice,
   52    * the first time setting the <code>lastPhase</code> flag to
   53    * <code>false</code>, and the second time setting it to <code>true</code>.
   54    * There may be any number of parties involved in a key exchange.
   55    *
   56    * @author Jan Luehe
   57    *
   58    * @see KeyGenerator
   59    * @see SecretKey
   60    * @since 1.4
   61    */
   62   
   63   public abstract class KeyAgreementSpi {
   64   
   65       /**
   66        * Initializes this key agreement with the given key and source of
   67        * randomness. The given key is required to contain all the algorithm
   68        * parameters required for this key agreement.
   69        *
   70        * <p> If the key agreement algorithm requires random bytes, it gets them
   71        * from the given source of randomness, <code>random</code>.
   72        * However, if the underlying
   73        * algorithm implementation does not require any random bytes,
   74        * <code>random</code> is ignored.
   75        *
   76        * @param key the party's private information. For example, in the case
   77        * of the Diffie-Hellman key agreement, this would be the party's own
   78        * Diffie-Hellman private key.
   79        * @param random the source of randomness
   80        *
   81        * @exception InvalidKeyException if the given key is
   82        * inappropriate for this key agreement, e.g., is of the wrong type or
   83        * has an incompatible algorithm type.
   84        */
   85       protected abstract void engineInit(Key key, SecureRandom random)
   86           throws InvalidKeyException;
   87   
   88       /**
   89        * Initializes this key agreement with the given key, set of
   90        * algorithm parameters, and source of randomness.
   91        *
   92        * @param key the party's private information. For example, in the case
   93        * of the Diffie-Hellman key agreement, this would be the party's own
   94        * Diffie-Hellman private key.
   95        * @param params the key agreement parameters
   96        * @param random the source of randomness
   97        *
   98        * @exception InvalidKeyException if the given key is
   99        * inappropriate for this key agreement, e.g., is of the wrong type or
  100        * has an incompatible algorithm type.
  101        * @exception InvalidAlgorithmParameterException if the given parameters
  102        * are inappropriate for this key agreement.
  103        */
  104       protected abstract void engineInit(Key key, AlgorithmParameterSpec params,
  105                                          SecureRandom random)
  106           throws InvalidKeyException, InvalidAlgorithmParameterException;
  107   
  108       /**
  109        * Executes the next phase of this key agreement with the given
  110        * key that was received from one of the other parties involved in this key
  111        * agreement.
  112        *
  113        * @param key the key for this phase. For example, in the case of
  114        * Diffie-Hellman between 2 parties, this would be the other party's
  115        * Diffie-Hellman public key.
  116        * @param lastPhase flag which indicates whether or not this is the last
  117        * phase of this key agreement.
  118        *
  119        * @return the (intermediate) key resulting from this phase, or null if
  120        * this phase does not yield a key
  121        *
  122        * @exception InvalidKeyException if the given key is inappropriate for
  123        * this phase.
  124        * @exception IllegalStateException if this key agreement has not been
  125        * initialized.
  126        */
  127       protected abstract Key engineDoPhase(Key key, boolean lastPhase)
  128           throws InvalidKeyException, IllegalStateException;
  129   
  130       /**
  131        * Generates the shared secret and returns it in a new buffer.
  132        *
  133        * <p>This method resets this <code>KeyAgreementSpi</code> object,
  134        * so that it
  135        * can be reused for further key agreements. Unless this key agreement is
  136        * reinitialized with one of the <code>engineInit</code> methods, the same
  137        * private information and algorithm parameters will be used for
  138        * subsequent key agreements.
  139        *
  140        * @return the new buffer with the shared secret
  141        *
  142        * @exception IllegalStateException if this key agreement has not been
  143        * completed yet
  144        */
  145       protected abstract byte[] engineGenerateSecret()
  146           throws IllegalStateException;
  147   
  148       /**
  149        * Generates the shared secret, and places it into the buffer
  150        * <code>sharedSecret</code>, beginning at <code>offset</code> inclusive.
  151        *
  152        * <p>If the <code>sharedSecret</code> buffer is too small to hold the
  153        * result, a <code>ShortBufferException</code> is thrown.
  154        * In this case, this call should be repeated with a larger output buffer.
  155        *
  156        * <p>This method resets this <code>KeyAgreementSpi</code> object,
  157        * so that it
  158        * can be reused for further key agreements. Unless this key agreement is
  159        * reinitialized with one of the <code>engineInit</code> methods, the same
  160        * private information and algorithm parameters will be used for
  161        * subsequent key agreements.
  162        *
  163        * @param sharedSecret the buffer for the shared secret
  164        * @param offset the offset in <code>sharedSecret</code> where the
  165        * shared secret will be stored
  166        *
  167        * @return the number of bytes placed into <code>sharedSecret</code>
  168        *
  169        * @exception IllegalStateException if this key agreement has not been
  170        * completed yet
  171        * @exception ShortBufferException if the given output buffer is too small
  172        * to hold the secret
  173        */
  174       protected abstract int engineGenerateSecret(byte[] sharedSecret,
  175                                                   int offset)
  176           throws IllegalStateException, ShortBufferException;
  177   
  178       /**
  179        * Creates the shared secret and returns it as a secret key object
  180        * of the requested algorithm type.
  181        *
  182        * <p>This method resets this <code>KeyAgreementSpi</code> object,
  183        * so that it
  184        * can be reused for further key agreements. Unless this key agreement is
  185        * reinitialized with one of the <code>engineInit</code> methods, the same
  186        * private information and algorithm parameters will be used for
  187        * subsequent key agreements.
  188        *
  189        * @param algorithm the requested secret key algorithm
  190        *
  191        * @return the shared secret key
  192        *
  193        * @exception IllegalStateException if this key agreement has not been
  194        * completed yet
  195        * @exception NoSuchAlgorithmException if the requested secret key
  196        * algorithm is not available
  197        * @exception InvalidKeyException if the shared secret key material cannot
  198        * be used to generate a secret key of the requested algorithm type (e.g.,
  199        * the key material is too short)
  200        */
  201       protected abstract SecretKey engineGenerateSecret(String algorithm)
  202           throws IllegalStateException, NoSuchAlgorithmException,
  203               InvalidKeyException;
  204   }

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