SharedSecureRandomImpl.java

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2011-2012 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package org.glassfish.security.common;

import java.security.SecureRandom;

/**
 * An utility class that supplies an Initialized SecureRandom.
 */
public class SharedSecureRandomImpl {

    //the generator has a large period (in Sun's standard implementation, based on the 160-bit SHA1 hash function, the period is 2^160);
    private static final SecureRandom secureRandom = new SecureRandom();

    static {
        //always call java.security.SecureRandom.nextBytes(byte[])
        //immediately after creating a new instance of the PRNG.
        //This will force the PRNG to seed itself securely
        byte[] key = new byte[20];
        secureRandom.nextBytes(key);
    }

    /**
     * Can a single  java.security.SecureRandom instance be shared  safely by multiple threads ?.
     * Yes.  As far as I know.  nextBytes and setSeed are sync'd.
     */
    public static SecureRandom get() {
        return secureRandom;
    }

}