mirror of git://gcc.gnu.org/git/gcc.git
100 lines
3.4 KiB
Java
100 lines
3.4 KiB
Java
/* ElGamalReceiver.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.javax.crypto.key.KeyAgreementException;
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import gnu.javax.crypto.key.IncomingMessage;
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import gnu.javax.crypto.key.OutgoingMessage;
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import java.math.BigInteger;
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import java.security.SecureRandom;
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import java.util.Map;
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import javax.crypto.interfaces.DHPrivateKey;
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/**
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* This implementation is the receiver's part of the ElGamal key agreement
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* exchange (B in [HAC]).
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*
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* @see ElGamalKeyAgreement
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*/
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public class ElGamalReceiver
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extends ElGamalKeyAgreement
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{
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/** The recipient's private key. */
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private DHPrivateKey B;
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// default 0-arguments constructor
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protected void engineInit(Map attributes) throws KeyAgreementException
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{
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rnd = (SecureRandom) attributes.get(SOURCE_OF_RANDOMNESS);
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// One-time setup (key generation and publication). Each user B generates
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// a keypair and publishes its public key
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B = (DHPrivateKey) attributes.get(KA_ELGAMAL_RECIPIENT_PRIVATE_KEY);
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if (B == null)
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throw new KeyAgreementException("missing recipient private key");
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}
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protected OutgoingMessage engineProcessMessage(IncomingMessage in)
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throws KeyAgreementException
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{
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switch (step)
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{
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case 0:
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return computeSharedSecret(in);
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default:
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throw new IllegalStateException("unexpected state");
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}
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}
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private OutgoingMessage computeSharedSecret(IncomingMessage in)
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throws KeyAgreementException
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{
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// (b) B computes the same key on receipt of message (1) as
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// K = (g^x)^xb mod p
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BigInteger m1 = in.readMPI();
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if (m1 == null)
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throw new KeyAgreementException("missing message (1)");
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ZZ = m1.modPow(B.getX(), B.getParams().getP()); // ZZ = (ya ^ xb) mod p
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complete = true;
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return null;
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}
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}
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