1 /*
   2  * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.security;
  27 
  28 /**
  29  * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
  30  * for the {@code SecureRandom} class.
  31  * All the abstract methods in this class must be implemented by each
  32  * service provider who wishes to supply the implementation
  33  * of a cryptographically strong pseudo-random number generator.
  34  *
  35  *
  36  * @see SecureRandom
  37  * @since 1.2
  38  */
  39 
  40 public abstract class SecureRandomSpi implements java.io.Serializable {
  41 
  42     private static final long serialVersionUID = -2991854161009191830L;
  43 
  44     /**
  45      * Reseeds this random object. The given seed supplements, rather than
  46      * replaces, the existing seed. Thus, repeated calls are guaranteed
  47      * never to reduce randomness.
  48      *
  49      * @param seed the seed.
  50      */
  51     protected abstract void engineSetSeed(byte[] seed);
  52 
  53     /**
  54      * Generates a user-specified number of random bytes.
  55      *
  56      * <p> If a call to {@code engineSetSeed} had not occurred previously,
  57      * the first call to this method forces this SecureRandom implementation
  58      * to seed itself.  This self-seeding will not occur if
  59      * {@code engineSetSeed} was previously called.
  60      *
  61      * @param bytes the array to be filled in with random bytes.
  62      */
  63     protected abstract void engineNextBytes(byte[] bytes);
  64 
  65     /**
  66      * Returns the given number of seed bytes.  This call may be used to
  67      * seed other random number generators.
  68      *
  69      * @param numBytes the number of seed bytes to generate.
  70      *
  71      * @return the seed bytes.
  72      */
  73      protected abstract byte[] engineGenerateSeed(int numBytes);
  74 }