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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/gnu/javax/crypto/key/dh/ElGamalReceiver.java
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+/* ElGamalReceiver.java --
+ Copyright (C) 2003, 2006 Free Software Foundation, Inc.
+
+This file is a part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or (at
+your option) any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
+USA
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package gnu.javax.crypto.key.dh;
+
+import gnu.javax.crypto.key.KeyAgreementException;
+import gnu.javax.crypto.key.IncomingMessage;
+import gnu.javax.crypto.key.OutgoingMessage;
+
+import java.math.BigInteger;
+import java.security.SecureRandom;
+import java.util.Map;
+
+import javax.crypto.interfaces.DHPrivateKey;
+
+/**
+ * This implementation is the receiver's part of the ElGamal key agreement
+ * exchange (B in [HAC]).
+ *
+ * @see ElGamalKeyAgreement
+ */
+public class ElGamalReceiver
+ extends ElGamalKeyAgreement
+{
+ /** The recipient's private key. */
+ private DHPrivateKey B;
+
+ // default 0-arguments constructor
+
+ protected void engineInit(Map attributes) throws KeyAgreementException
+ {
+ rnd = (SecureRandom) attributes.get(SOURCE_OF_RANDOMNESS);
+ // One-time setup (key generation and publication). Each user B generates
+ // a keypair and publishes its public key
+ B = (DHPrivateKey) attributes.get(KA_ELGAMAL_RECIPIENT_PRIVATE_KEY);
+ if (B == null)
+ throw new KeyAgreementException("missing recipient private key");
+ }
+
+ protected OutgoingMessage engineProcessMessage(IncomingMessage in)
+ throws KeyAgreementException
+ {
+ switch (step)
+ {
+ case 0:
+ return computeSharedSecret(in);
+ default:
+ throw new IllegalStateException("unexpected state");
+ }
+ }
+
+ private OutgoingMessage computeSharedSecret(IncomingMessage in)
+ throws KeyAgreementException
+ {
+ // (b) B computes the same key on receipt of message (1) as
+ // K = (g^x)^xb mod p
+ BigInteger m1 = in.readMPI();
+ if (m1 == null)
+ throw new KeyAgreementException("missing message (1)");
+ ZZ = m1.modPow(B.getX(), B.getParams().getP()); // ZZ = (ya ^ xb) mod p
+ complete = true;
+ return null;
+ }
+}