package gnu.crypto.key.srp6;
// ----------------------------------------------------------------------------
// $Id: SRPPrivateKey.java,v 1.2 2005/10/06 04:24:16 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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 Crypto 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 this program; 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.
// ----------------------------------------------------------------------------
import gnu.crypto.Registry;
import gnu.crypto.key.IKeyPairCodec;
import java.math.BigInteger;
import java.security.PrivateKey;
/**
* <p>A representation of an SRP ephemeral private key.</p>
*
* <p>Reference:</p>
* <ol>
* <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br>
* Thomas J. Wu.</li>
* </ol>
*
* @version $Revision: 1.2 $
*/
public class SRPPrivateKey extends SRPKey implements PrivateKey {
// Constants and variables
// -------------------------------------------------------------------------
/**
* The private exponent for either the server or the client engaged in the
* SRP protocol exchange.
*/
private final BigInteger X;
/**
* The user's verifier (v) --for the server-- also computed at the client
* side as g.modPow(x, N), where x is the hashed output of the user name and
* password .
*/
private final BigInteger v;
// Constructor(s)
// -------------------------------------------------------------------------
/**
* <p>Public constructor for use from outside this package.</p>
*
* @param N the public shared modulus.
* @param g the generator.
* @param x the private exponent of the ephemeral key.
*/
public SRPPrivateKey(BigInteger N, BigInteger g, BigInteger x) {
this(N, g, x, null);
}
/**
* <p>Public constructor for use from outside this package.</p>
*
* @param N the public shared modulus.
* @param g the generator.
* @param x the private exponent of the ephemeral key.
* @param v the user's verifier value (for the server side only).
*/
public SRPPrivateKey(BigInteger N, BigInteger g, BigInteger x, BigInteger v) {
super(N, g);
SRPAlgorithm.checkParams(N, g);
this.X = x;
this.v = v;
}
/**
* <p>Default constructor. Assumes N and g are already validated.</p>
*
* @param params an array of either 3 or 4 values representing N, g, and
* either v and X for the server, or just X for the client. Those values
* represent the following:
* <ol>
* <li>v (server side): the user's verifier.</li>
* <li>X (both sides): the server's or client's ephemeral private exponent.</li>
* </ol>
*/
SRPPrivateKey(BigInteger[] params) {
super(params[0], params[1]);
if (params.length == 3) {
X = params[2];
v = null;
} else if (params.length == 4) {
X = params[2];
v = params[3];
} else {
throw new IllegalArgumentException("invalid number of SRP parameters");
}
}
// Class methods
// -------------------------------------------------------------------------
/**
* <p>A class method that takes the output of the <code>encodePrivateKey()</code>
* method of an SRP keypair codec object (an instance implementing
* {@link IKeyPairCodec} for DSS keys, and re-constructs an instance of this
* object.</p>
*
* @param k the contents of a previously encoded instance of this object.
* @throws ArrayIndexOutOfBoundsException if there is not enough bytes, in
* <code>k</code>, to represent a valid encoding of an instance of this object.
* @throws IllegalArgumentException if the byte sequence does not represent a
* valid encoding of an instance of this object.
*/
public static SRPPrivateKey valueOf(byte[] k) {
// check magic...
// we should parse here enough bytes to know which codec to use, and
// direct the byte array to the appropriate codec. since we only have one
// codec, we could have immediately tried it; nevertheless since testing
// one byte is cheaper than instatiating a codec that will fail we test
// the first byte before we carry on.
if (k[0] == Registry.MAGIC_RAW_SRP_PRIVATE_KEY[0]) {
// it's likely to be in raw format. get a raw codec and hand it over
IKeyPairCodec codec = new SRPKeyPairRawCodec();
return (SRPPrivateKey) codec.decodePrivateKey(k);
} else {
throw new IllegalArgumentException("magic");
}
}
// Instance methods
// -------------------------------------------------------------------------
/**
* <p>Returns the private exponent of the key as a {@link BigInteger}.</p>
*
* @return the private exponent of the key as a {@link BigInteger}.
*/
public BigInteger getX() {
return X;
}
/**
* <p>Returns the user's verifier as a {@link BigInteger}.</p>
*
* @return the user's verifier as a {@link BigInteger} if this is an SRP
* private key of a Host, or <code>null</code> if this is a private SRP key
* for a User.
*/
public BigInteger getV() {
return v;
}
// Other instance methods --------------------------------------------------
/**
* <p>Returns the encoded form of this private key according to the
* designated format.</p>
*
* @param format the desired format identifier of the resulting encoding.
* @return the byte sequence encoding this key according to the designated
* format.
* @throws IllegalArgumentException if the format is not supported.
*/
public byte[] getEncoded(int format) {
byte[] result;
switch (format) {
case IKeyPairCodec.RAW_FORMAT:
result = new SRPKeyPairRawCodec().encodePrivateKey(this);
break;
default:
throw new IllegalArgumentException("format");
}
return result;
}
/**
* <p>Returns <code>true</code> if the designated object is an instance of
* <code>SRPPrivateKey</code> and has the same SRP parameter values as this
* one.</p>
*
* @param obj the other non-null SRP key to compare to.
* @return <code>true</code> if the designated object is of the same type and
* value as this one.
*/
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (!(obj instanceof SRPPrivateKey)) {
return false;
}
SRPPrivateKey that = (SRPPrivateKey) obj;
boolean result = super.equals(that) && X.equals(that.getX());
if (v != null) {
result = result && v.equals(that.getV());
}
return result;
}
}