Source for gnu.javax.crypto.key.dh.DiffieHellmanKeyAgreement

   1: /* DiffieHellmanKeyAgreement.java --
   2:    Copyright (C) 2003, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is a 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 of the License, or (at
   9: your option) 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; if not, write to the Free Software
  18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19: 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.key.dh;
  40: 
  41: import gnu.java.security.Registry;
  42: import gnu.java.security.util.Util;
  43: 
  44: import gnu.javax.crypto.key.BaseKeyAgreementParty;
  45: import gnu.javax.crypto.key.KeyAgreementException;
  46: 
  47: import java.math.BigInteger;
  48: 
  49: import javax.crypto.interfaces.DHPrivateKey;
  50: 
  51: /**
  52:  * The basic version of the Diffie-Hellman key agreement is described in the
  53:  * Handbook of Applied Cryptography [HAC] as follows:
  54:  * <ul>
  55:  * <li>An appropriate prime p and generator g of Z<sub>p</sub><sup>*</sup>
  56:  * (2 &lt;= g &lt;= p-2) are selected and published.</li>
  57:  * <li>A and B each send the other one message over an open channel; as a
  58:  * result, they both can then compute a shared secret key K which they can use
  59:  * to protect their future communication.</li>
  60:  * <li>A chooses a random secret x, 1 &lt;= x &lt;= p-2, and sends B message
  61:  * (1) which is g^x mod p.</li>
  62:  * <li>B chooses a random secret y, 1 &lt;= y &lt;= p-2, and sends A message
  63:  * (2) which is g^y mod p.</li>
  64:  * <li>B receives message (1) and computes the shared key as K = (g^x)^y mod p.
  65:  * </li>
  66:  * <li>A receives message (2) and computes the shared key as K = (g^y)^x mod p.
  67:  * </li>
  68:  * </ul>
  69:  * <p>
  70:  * RFC-2631 describes a <i>Static-Static Mode</i> of operations with
  71:  * Diffie-Hellman keypairs as follows:
  72:  * <pre>
  73:  *  &quot;In Static-Static mode, both the sender and the recipient have a
  74:  *  static (and certified) key pair. Since the sender's and recipient's
  75:  *  keys are therefore the same for each message, ZZ will be the same for
  76:  *  each message. Thus, partyAInfo MUST be used (and different for each
  77:  *  message) in order to ensure that different messages use different
  78:  *  KEKs. Implementations MAY implement Static-Static mode.&quot;
  79:  * </pre>
  80:  *
  81:  * <p>
  82:  * Reference:
  83:  * <ol>
  84:  * <li><a href="http://www.ietf.org/rfc/rfc2631.txt">Diffie-Hellman Key
  85:  * Agreement Method</a><br>
  86:  * Eric Rescorla.</li>
  87:  * <li><a href="http://www.cacr.math.uwaterloo.ca/hac">[HAC]</a>: Handbook of
  88:  * Applied Cryptography.<br>
  89:  * CRC Press, Inc. ISBN 0-8493-8523-7, 1997<br>
  90:  * Menezes, A., van Oorschot, P. and S. Vanstone.</li>
  91:  * </ol>
  92:  */
  93: public abstract class DiffieHellmanKeyAgreement
  94:     extends BaseKeyAgreementParty
  95: {
  96:   public static final String SOURCE_OF_RANDOMNESS = "gnu.crypto.dh.ka.prng";
  97:   public static final String KA_DIFFIE_HELLMAN_OWNER_PRIVATE_KEY =
  98:       "gnu.crypto.dh.ka.owner.private.key";
  99:   /** The key agreement party's private key. */
 100:   protected DHPrivateKey ownerKey;
 101:   /** The shared secret key. */
 102:   protected BigInteger ZZ;
 103: 
 104:   protected DiffieHellmanKeyAgreement()
 105:   {
 106:     super(Registry.DH_KA);
 107:   }
 108: 
 109:   protected byte[] engineSharedSecret() throws KeyAgreementException
 110:   {
 111:     return Util.trim(ZZ);
 112:   }
 113: 
 114:   protected void engineReset()
 115:   {
 116:     ownerKey = null;
 117:     ZZ = null;
 118:   }
 119: }