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diff --git a/libjava/classpath/gnu/javax/crypto/jce/DiffieHellmanImpl.java b/libjava/classpath/gnu/javax/crypto/jce/DiffieHellmanImpl.java
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+/* DiffieHellmanImpl.java -- implementation of the Diffie-Hellman key agreement.
+   Copyright (C) 2005, 2006  Free Software Foundation, Inc.
+
+This file is 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, 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; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, 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.jce;
+
+import java.math.BigInteger;
+import java.security.InvalidKeyException;
+import java.security.Key;
+import java.security.SecureRandom;
+import java.security.spec.AlgorithmParameterSpec;
+
+import javax.crypto.KeyAgreementSpi;
+import javax.crypto.SecretKey;
+import javax.crypto.ShortBufferException;
+import javax.crypto.interfaces.DHPrivateKey;
+import javax.crypto.interfaces.DHPublicKey;
+import javax.crypto.spec.DHParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+
+/**
+ * The JCE implementation of a 2-party Diffie-Hellman key agreement.
+ *
+ * @author Casey Marshall (csm@gnu.org)
+ */
+public final class DiffieHellmanImpl
+    extends KeyAgreementSpi
+{
+  /** The private key being used for this agreement. */
+  private DHPrivateKey key;
+
+  /** The current result. */
+  private byte[] result;
+
+  /** True if the caller told us we are done. */
+  private boolean last_phase_done;
+
+  /** Trivial default constructor. */
+  public DiffieHellmanImpl()
+  {
+    super();
+
+    key = null;
+    result = null;
+    last_phase_done = false;
+  }
+
+  protected Key engineDoPhase(Key incoming, boolean lastPhase)
+      throws InvalidKeyException
+  {
+    if (key == null)
+      throw new IllegalStateException("Not initialized");
+
+    if (last_phase_done)
+      throw new IllegalStateException("Last phase already done");
+
+    if (! (incoming instanceof DHPublicKey))
+      throw new InvalidKeyException("Key MUST be a DHPublicKey");
+
+    DHPublicKey pub = (DHPublicKey) incoming;
+    DHParameterSpec s1 = key.getParams();
+    DHParameterSpec s2 = pub.getParams();
+    if (! s1.getG().equals(s2.getG()) || ! s1.getP().equals(s2.getP()))
+      throw new InvalidKeyException("Incompatible key");
+    if (! lastPhase)
+      throw new IllegalArgumentException(
+          "This key-agreement MUST be concluded in one step only");
+    BigInteger resultBI = pub.getY().modPow(key.getX(), s1.getP());
+    result = resultBI.toByteArray();
+    if (result[0] == 0x00)
+      {
+        byte[] buf = new byte[result.length - 1];
+        System.arraycopy(result, 1, buf, 0, buf.length);
+        result = buf;
+      }
+    last_phase_done = true;
+    return null;
+  }
+
+  protected byte[] engineGenerateSecret()
+  {
+    checkState();
+    byte[] res = (byte[]) result.clone();
+    reset();
+    return res;
+  }
+
+  protected int engineGenerateSecret(byte[] secret, int offset)
+      throws ShortBufferException
+  {
+    checkState();
+    if (result.length > secret.length - offset)
+      throw new ShortBufferException();
+    System.arraycopy(result, 0, secret, offset, result.length);
+    int res = result.length;
+    reset();
+    return res;
+  }
+
+  protected SecretKey engineGenerateSecret(String algorithm)
+      throws InvalidKeyException
+  {
+    checkState();
+    byte[] s = (byte[]) result.clone();
+    SecretKey res = new SecretKeySpec(s, algorithm);
+    reset();
+    return res;
+  }
+
+  protected void engineInit(Key key, SecureRandom random)
+      throws InvalidKeyException
+  {
+    if (! (key instanceof DHPrivateKey))
+      throw new InvalidKeyException("Key MUST be a DHPrivateKey");
+    this.key = (DHPrivateKey) key;
+    reset();
+  }
+
+  protected void engineInit(Key key, AlgorithmParameterSpec params,
+                            SecureRandom random)
+      throws InvalidKeyException
+  {
+    engineInit(key, random);
+  }
+
+  private void reset()
+  {
+    result = null;
+    last_phase_done = false;
+  }
+
+  private void checkState()
+  {
+    if (result == null || ! last_phase_done)
+      throw new IllegalStateException("Not finished");
+  }
+}