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package gnu.crypto.key.dss;
// ----------------------------------------------------------------------------
// $Id: DSSPublicKey.java,v 1.1 2003/09/26 23:50:48 raif Exp $
//
// Copyright (C) 2001, 2002, 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.,
// 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.
// ----------------------------------------------------------------------------
import gnu.crypto.Registry;
import gnu.crypto.key.IKeyPairCodec;
import java.math.BigInteger;
import java.security.PublicKey;
import java.security.interfaces.DSAPublicKey;
/**
* An object that embodies a DSS (Digital Signature Standard) public key.
*
* @version $Revision: 1.1 $
* @see #getEncoded
*/
public class DSSPublicKey extends DSSKey implements PublicKey, DSAPublicKey {
// Constants and variables
// -------------------------------------------------------------------------
/**
* y = gx mod p where x is the private
* part of the DSA key.
*/
private final BigInteger y;
// Constructor(s)
// -------------------------------------------------------------------------
/**
* Trivial constructor.
*
* @param p the public modulus.
* @param q the public prime divisor of p-1.
* @param g a generator of the unique cyclic group Z*
* p.
* @param y the public key part.
*/
public DSSPublicKey(BigInteger p, BigInteger q, BigInteger g, BigInteger y) {
super(p, q, g);
this.y = y;
}
// Class methods
// -------------------------------------------------------------------------
/**
* A class method that takes the output of the encodePublicKey()
* method of a DSS keypair codec object (an instance implementing
* {@link gnu.crypto.key.IKeyPairCodec} for DSS keys, and re-constructs an
* instance of this object.
*
* @param k the contents of a previously encoded instance of this object.
* @exception ArrayIndexOutOfBoundsException if there is not enough bytes,
* in k, to represent a valid encoding of an instance of
* this object.
* @exception IllegalArgumentException if the byte sequence does not
* represent a valid encoding of an instance of this object.
*/
public static DSSPublicKey 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_DSS_PUBLIC_KEY[0]) {
// it's likely to be in raw format. get a raw codec and hand it over
IKeyPairCodec codec = new DSSKeyPairRawCodec();
return (DSSPublicKey) codec.decodePublicKey(k);
} else {
throw new IllegalArgumentException("magic");
}
}
// Instance methods
// -------------------------------------------------------------------------
// java.security.interfaces.DSAPublicKey interface implementation ----------
public BigInteger getY() {
return y;
}
// Other instance methods --------------------------------------------------
/**
* Returns the encoded form of this public key according to the designated
* format.
*
* @param format the desired format identifier of the resulting encoding.
* @return the byte sequence encoding this key according to the designated
* format.
* @exception IllegalArgumentException if the format is not supported.
* @see DSSKeyPairRawCodec
*/
public byte[] getEncoded(int format) {
byte[] result;
switch (format) {
case IKeyPairCodec.RAW_FORMAT:
result = new DSSKeyPairRawCodec().encodePublicKey(this);
break;
default:
throw new IllegalArgumentException("format");
}
return result;
}
/**
* Returns true if the designated object is an instance of
* {@link DSAPublicKey} and has the same DSS (Digital Signature Standard)
* parameter values as this one.
*
* @param obj the other non-null DSS key to compare to.
* @return true 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 DSAPublicKey)) {
return false;
}
DSAPublicKey that = (DSAPublicKey) obj;
return super.equals(that) && y.equals(that.getY());
}
}
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