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jeremybenn |
/* SRPPublicKey.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.srp6;
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import gnu.java.security.Registry;
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import gnu.java.security.key.IKeyPairCodec;
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import java.math.BigInteger;
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import java.security.PublicKey;
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/**
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* A representation of an SRP ephemeral public key.
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* <p>
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* Reference:
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* <ol>
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* <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br>
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* Thomas J. Wu.</li>
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* </ol>
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*/
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public class SRPPublicKey
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extends SRPKey
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implements PublicKey
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{
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/**
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* The public exponent for either the server or the client engaged in the SRP
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* protocol exchange.
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*/
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private final BigInteger Y;
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/**
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* Public constructor for use from outside this package.
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*
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* @param N the public shared modulus.
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* @param g the generator.
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* @param Y the public exponent of the ephemeral key.
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*/
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public SRPPublicKey(BigInteger N, BigInteger g, BigInteger Y)
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{
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super(N, g);
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SRPAlgorithm.checkParams(N, g);
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this.Y = Y;
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}
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/**
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* Default constructor. Assumes that N and g are already validated.
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*
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* @param params an array of 3 values representing N, g and Y; the latter
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* being the client's or server's public exponent.
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*/
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SRPPublicKey(BigInteger[] params)
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{
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super(params[0], params[1]);
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this.Y = params[2];
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}
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/**
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* A class method that takes the output of the <code>encodePublicKey()</code>
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* method of an SRP keypair codec object (an instance implementing
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* {@link IKeyPairCodec} for SRP keys, and re-constructs an instance of this
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* object.
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*
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* @param k the contents of a previously encoded instance of this object.
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* @throws ArrayIndexOutOfBoundsException if there is not enough bytes, in
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* <code>k</code>, to represent a valid encoding of an instance
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* of this object.
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* @throws IllegalArgumentException if the byte sequence does not represent a
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* valid encoding of an instance of this object.
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*/
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public static SRPPublicKey valueOf(byte[] k)
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{
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// check magic...
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// we should parse here enough bytes to know which codec to use, and
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// direct the byte array to the appropriate codec. since we only have one
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// codec, we could have immediately tried it; nevertheless since testing
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// one byte is cheaper than instatiating a codec that will fail we test
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// the first byte before we carry on.
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if (k[0] == Registry.MAGIC_RAW_SRP_PUBLIC_KEY[0])
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{
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// it's likely to be in raw format. get a raw codec and hand it over
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IKeyPairCodec codec = new SRPKeyPairRawCodec();
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return (SRPPublicKey) codec.decodePublicKey(k);
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}
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throw new IllegalArgumentException("magic");
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}
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/**
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* Returns the public exponent of the key as a {@link BigInteger}.
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*
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* @return the public exponent of the key as a {@link BigInteger}.
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*/
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public BigInteger getY()
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{
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return Y;
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}
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/**
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* Returns the encoded form of this public key according to the designated
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* format.
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*
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* @param format the desired format identifier of the resulting encoding.
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* @return the byte sequence encoding this key according to the designated
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* format.
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* @throws IllegalArgumentException if the format is not supported.
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*/
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public byte[] getEncoded(int format)
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{
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byte[] result;
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switch (format)
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{
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case IKeyPairCodec.RAW_FORMAT:
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result = new SRPKeyPairRawCodec().encodePublicKey(this);
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break;
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default:
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throw new IllegalArgumentException("format");
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}
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return result;
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}
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/**
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* Returns <code>true</code> if the designated object is an instance of
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* <code>SRPPublicKey</code>and has the same SRP parameter values as this
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* one.
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*
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* @param obj the other non-null SRP key to compare to.
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* @return <code>true</code> if the designated object is of the same type
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* and value as this one.
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*/
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public boolean equals(Object obj)
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{
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if (obj == null)
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return false;
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if (! (obj instanceof SRPPublicKey))
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return false;
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SRPPublicKey that = (SRPPublicKey) obj;
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return super.equals(that) && Y.equals(that.getY());
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}
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}
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