libjava/classpath/gnu/javax/crypto/jce/DiffieHellmanImpl.java

   1 /* DiffieHellmanImpl.java -- implementation of the Diffie-Hellman key agreement.
   2    Copyright (C) 2005, 2006  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., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 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
  39 package gnu.javax.crypto.jce;
  40
  41 import java.math.BigInteger;
  42 import java.security.InvalidKeyException;
  43 import java.security.Key;
  44 import java.security.SecureRandom;
  45 import java.security.spec.AlgorithmParameterSpec;
  46
  47 import javax.crypto.KeyAgreementSpi;
  48 import javax.crypto.SecretKey;
  49 import javax.crypto.interfaces.DHPrivateKey;
  50 import javax.crypto.interfaces.DHPublicKey;
  51 import javax.crypto.spec.DHParameterSpec;
  52 import javax.crypto.spec.SecretKeySpec;
  53
  54 /**
  55  * The JCE implementation of a 2-party Diffie-Hellman key agreement.
  56  *
  57  * @author Casey Marshall (csm@gnu.org)
  58  */
  59 public final class DiffieHellmanImpl
  60     extends KeyAgreementSpi
  61 {
  62   /** The private key being used for this agreement. */
  63   private DHPrivateKey key;
  64
  65   /** The current result. */
  66   private BigInteger result;
  67
  68   /** True if the caller told us we are done. */
  69   private boolean last_phase_done;
  70
  71   /** Trivial default constructor. */
  72   public DiffieHellmanImpl()
  73   {
  74     super();
  75
  76     key = null;
  77     result = null;
  78     last_phase_done = false;
  79   }
  80
  81   protected Key engineDoPhase(Key incoming, boolean lastPhase)
  82       throws InvalidKeyException
  83   {
  84     if (key == null)
  85       throw new IllegalStateException("Not initialized");
  86
  87     if (last_phase_done)
  88       throw new IllegalStateException("Last phase already done");
  89
  90     if (! (incoming instanceof DHPublicKey))
  91       throw new InvalidKeyException("Key MUST be a DHPublicKey");
  92
  93     DHPublicKey pub = (DHPublicKey) incoming;
  94     DHParameterSpec s1 = key.getParams();
  95     DHParameterSpec s2 = pub.getParams();
  96     if (! s1.getG().equals(s2.getG()) || ! s1.getP().equals(s2.getP())
  97         || s1.getL() != s2.getL())
  98       throw new InvalidKeyException("Incompatible key");
  99
 100     result = pub.getY().modPow(key.getX(), s1.getP());
 101     if (! lastPhase)
 102       throw new IllegalArgumentException("This key-agreement MUST be concluded in one step only");
 103
 104     last_phase_done = true;
 105     return null;
 106   }
 107
 108   protected byte[] engineGenerateSecret()
 109   {
 110     if (result == null || ! last_phase_done)
 111       throw new IllegalStateException("Not finished");
 112
 113     byte[] buf = result.toByteArray();
 114     if (buf[0] == 0x00)
 115       {
 116         byte[] buf2 = new byte[buf.length - 1];
 117         System.arraycopy(buf, 1, buf2, 0, buf2.length);
 118         buf = buf2;
 119       }
 120
 121     return buf;
 122   }
 123
 124   protected int engineGenerateSecret(byte[] secret, int offset)
 125   {
 126     byte[] s = engineGenerateSecret();
 127     System.arraycopy(s, 0, secret, offset, s.length);
 128     return s.length;
 129   }
 130
 131   protected SecretKey engineGenerateSecret(String algorithm)
 132       throws InvalidKeyException
 133   {
 134     byte[] s = engineGenerateSecret();
 135     return new SecretKeySpec(s, algorithm);
 136   }
 137
 138   protected void engineInit(Key key, SecureRandom random)
 139       throws InvalidKeyException
 140   {
 141     if (! (key instanceof DHPrivateKey))
 142       throw new InvalidKeyException("Key MUST be a DHPrivateKey");
 143
 144     this.key = (DHPrivateKey) key;
 145     result = null;
 146     last_phase_done = false;
 147   }
 148
 149   protected void engineInit(Key key, AlgorithmParameterSpec params,
 150                             SecureRandom random)
 151       throws InvalidKeyException
 152   {
 153     engineInit(key, random);
 154   }
 155 }