/* DiffieHellmanImpl.java -- implementation of the Diffie-Hellman key agreement. Copyright (C) 2005 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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; import gnu.java.security.provider.GnuDHPublicKey; import java.math.BigInteger; import java.security.Key; import java.security.InvalidKeyException; import java.security.PrivateKey; import java.security.PublicKey; import java.security.SecureRandom; import java.security.spec.AlgorithmParameterSpec; import javax.crypto.KeyAgreementSpi; import javax.crypto.SecretKey; import javax.crypto.interfaces.DHPrivateKey; import javax.crypto.interfaces.DHPublicKey; import javax.crypto.spec.DHParameterSpec; import javax.crypto.spec.SecretKeySpec; /** * The 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 random-number generator used to generate secrets. */ private SecureRandom random; /** The current result. */ private BigInteger result; /** True if the caller told us we are done. */ private boolean last_phase_done; /** Trivial default constructor. */ public DiffieHellmanImpl () { key = null; random = null; result = null; last_phase_done = false; } // KeyAgreementSpi methods. protected Key engineDoPhase (final Key incoming, final 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 ("expecting javax.crypto.interfaces.DHPublicKey"); DHPublicKey pub = (DHPublicKey) incoming; DHParameterSpec s1 = key.getParams(); DHParameterSpec s2 = key.getParams(); if (!s1.getG().equals (s2.getG()) || !s1.getP().equals (s2.getP()) || s1.getL() != s2.getL()) throw new InvalidKeyException ("supplied key is not compatible"); BigInteger randval = new BigInteger (s1.getL(), random); BigInteger out = s1.getG().modPow (key.getX(), s1.getP()); if (result == null) result = s1.getG(); result = result.modPow (pub.getY(), s1.getP()); if (lastPhase) { last_phase_done = true; return null; } return new GnuDHPublicKey (s1, out, null); } protected byte[] engineGenerateSecret () { if (result == null || !last_phase_done) throw new IllegalStateException ("not finished"); byte[] buf = result.toByteArray (); if (buf[0] == 0x00) { byte[] buf2 = new byte[buf.length - 1]; System.arraycopy (buf, 1, buf2, 0, buf2.length); buf = buf2; } return buf; } protected int engineGenerateSecret (final byte[] secret, final int offset) { byte[] s = engineGenerateSecret(); System.arraycopy (s, 0, secret, offset, s.length); return s.length; } protected SecretKey engineGenerateSecret (final String algorithm) throws InvalidKeyException { byte[] s = engineGenerateSecret(); return new SecretKeySpec (s, algorithm); } protected void engineInit (final Key key, final SecureRandom random) throws InvalidKeyException { if (!(key instanceof DHPrivateKey)) throw new InvalidKeyException ("not a javax.crypto.interfaces.DHPrivateKey"); this.key = (DHPrivateKey) key; if (random != null) this.random = random; else if (this.random == null) this.random = new SecureRandom(); result = null; last_phase_done = false; } protected void engineInit (final Key key, final AlgorithmParameterSpec params, final SecureRandom random) throws InvalidKeyException { engineInit (key, random); } }