Java example source code file (DSAPublicKey.java)

This example Java source code file (DSAPublicKey.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

algiddsa, algorithmparameters, biginteger, der, derinputstream, dsaparameterspec, dsaparams, dsapublickey, invalidkeyexception, ioexception, math, security, serializable, string, sun, util, x509key

The DSAPublicKey.java Java example source code

/*
 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.security.provider;

import java.util.*;
import java.io.*;
import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.security.ProviderException;
import java.security.AlgorithmParameters;
import java.security.spec.DSAParameterSpec;
import java.security.spec.InvalidParameterSpecException;
import java.security.interfaces.DSAParams;

import sun.security.x509.X509Key;
import sun.security.x509.AlgIdDSA;
import sun.security.util.BitArray;
import sun.security.util.Debug;
import sun.security.util.DerValue;
import sun.security.util.DerInputStream;
import sun.security.util.DerOutputStream;

/**
 * An X.509 public key for the Digital Signature Algorithm.
 *
 * @author Benjamin Renaud
 *
 *
 * @see DSAPrivateKey
 * @see AlgIdDSA
 * @see DSA
 */

public class DSAPublicKey extends X509Key
implements java.security.interfaces.DSAPublicKey, Serializable {

    /** use serialVersionUID from JDK 1.1. for interoperability */
    private static final long serialVersionUID = -2994193307391104133L;

    /* the public key */
    private BigInteger y;

    /*
     * Keep this constructor for backwards compatibility with JDK1.1.
     */
    public DSAPublicKey() {
    }

    /**
     * Make a DSA public key out of a public key and three parameters.
     * The p, q, and g parameters may be null, but if so, parameters will need
     * to be supplied from some other source before this key can be used in
     * cryptographic operations.  PKIX RFC2459bis explicitly allows DSA public
     * keys without parameters, where the parameters are provided in the
     * issuer's DSA public key.
     *
     * @param y the actual key bits
     * @param p DSA parameter p, may be null if all of p, q, and g are null.
     * @param q DSA parameter q, may be null if all of p, q, and g are null.
     * @param g DSA parameter g, may be null if all of p, q, and g are null.
     */
    public DSAPublicKey(BigInteger y, BigInteger p, BigInteger q,
                        BigInteger g)
    throws InvalidKeyException {
        this.y = y;
        algid = new AlgIdDSA(p, q, g);

        try {
            byte[] keyArray = new DerValue(DerValue.tag_Integer,
                               y.toByteArray()).toByteArray();
            setKey(new BitArray(keyArray.length*8, keyArray));
            encode();
        } catch (IOException e) {
            throw new InvalidKeyException("could not DER encode y: " +
                                          e.getMessage());
        }
    }

    /**
     * Make a DSA public key from its DER encoding (X.509).
     */
    public DSAPublicKey(byte[] encoded) throws InvalidKeyException {
        decode(encoded);
    }

    /**
     * Returns the DSA parameters associated with this key, or null if the
     * parameters could not be parsed.
     */
    public DSAParams getParams() {
        try {
            if (algid instanceof DSAParams) {
                return (DSAParams)algid;
            } else {
                DSAParameterSpec paramSpec;
                AlgorithmParameters algParams = algid.getParameters();
                if (algParams == null) {
                    return null;
                }
                paramSpec = algParams.getParameterSpec(DSAParameterSpec.class);
                return (DSAParams)paramSpec;
            }
        } catch (InvalidParameterSpecException e) {
            return null;
        }
    }

    /**
     * Get the raw public value, y, without the parameters.
     *
     * @see getParameters
     */
    public BigInteger getY() {
        return y;
    }

    public String toString() {
        return "Sun DSA Public Key\n    Parameters:" + algid
            + "\n  y:\n" + Debug.toHexString(y) + "\n";
    }

    protected void parseKeyBits() throws InvalidKeyException {
        try {
            DerInputStream in = new DerInputStream(getKey().toByteArray());
            y = in.getBigInteger();
        } catch (IOException e) {
            throw new InvalidKeyException("Invalid key: y value\n" +
                                          e.getMessage());
        }
    }
}