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jeremybenn |
/* DiffieHellmanKeyAgreement.java --
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Copyright (C) 2003, 2006 Free Software Foundation, Inc.
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This file is a part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at
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your option) any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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USA
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.javax.crypto.key.dh;
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import gnu.java.security.Registry;
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import gnu.java.security.util.Util;
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import gnu.javax.crypto.key.BaseKeyAgreementParty;
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import gnu.javax.crypto.key.KeyAgreementException;
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import java.math.BigInteger;
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import javax.crypto.interfaces.DHPrivateKey;
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/**
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* The basic version of the Diffie-Hellman key agreement is described in the
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* Handbook of Applied Cryptography [HAC] as follows:
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* <ul>
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* <li>An appropriate prime p and generator g of Z<sub>p</sub><sup>*</sup>
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* (2 <= g <= p-2) are selected and published.</li>
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* <li>A and B each send the other one message over an open channel; as a
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* result, they both can then compute a shared secret key K which they can use
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* to protect their future communication.</li>
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* <li>A chooses a random secret x, 1 <= x <= p-2, and sends B message
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* (1) which is g^x mod p.</li>
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* <li>B chooses a random secret y, 1 <= y <= p-2, and sends A message
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* (2) which is g^y mod p.</li>
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* <li>B receives message (1) and computes the shared key as K = (g^x)^y mod p.
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* </li>
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* <li>A receives message (2) and computes the shared key as K = (g^y)^x mod p.
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* </li>
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* </ul>
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* <p>
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* RFC-2631 describes a <i>Static-Static Mode</i> of operations with
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* Diffie-Hellman keypairs as follows:
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* <pre>
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* "In Static-Static mode, both the sender and the recipient have a
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* static (and certified) key pair. Since the sender's and recipient's
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* keys are therefore the same for each message, ZZ will be the same for
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* each message. Thus, partyAInfo MUST be used (and different for each
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* message) in order to ensure that different messages use different
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* KEKs. Implementations MAY implement Static-Static mode."
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* </pre>
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*
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* <p>
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* Reference:
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* <ol>
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* <li><a href="http://www.ietf.org/rfc/rfc2631.txt">Diffie-Hellman Key
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* Agreement Method</a><br>
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* Eric Rescorla.</li>
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* <li><a href="http://www.cacr.math.uwaterloo.ca/hac">[HAC]</a>: Handbook of
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* Applied Cryptography.<br>
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* CRC Press, Inc. ISBN 0-8493-8523-7, 1997<br>
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* Menezes, A., van Oorschot, P. and S. Vanstone.</li>
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* </ol>
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*/
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public abstract class DiffieHellmanKeyAgreement
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extends BaseKeyAgreementParty
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{
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public static final String SOURCE_OF_RANDOMNESS = "gnu.crypto.dh.ka.prng";
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public static final String KA_DIFFIE_HELLMAN_OWNER_PRIVATE_KEY =
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"gnu.crypto.dh.ka.owner.private.key";
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/** The key agreement party's private key. */
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protected DHPrivateKey ownerKey;
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/** The shared secret key. */
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protected BigInteger ZZ;
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protected DiffieHellmanKeyAgreement()
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{
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super(Registry.DH_KA);
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}
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protected byte[] engineSharedSecret() throws KeyAgreementException
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{
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return Util.trim(ZZ);
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}
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protected void engineReset()
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{
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ownerKey = null;
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ZZ = null;
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}
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}
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