irandom.java

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/* IRandom.java -- 
   Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath 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 of the License, or (at
your option) any later version.

GNU Classpath 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 GNU Classpath; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, 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.  */


package gnu.java.security.prng;

import java.util.Map;

/**
 * <p>The basic visible methods of any pseudo-random number generator.</p>
 *
 * <p>The [HAC] defines a PRNG (as implemented in this library) as follows:</p>
 *
 * <ul>
 *    <li>"5.6 Definition: A pseudorandom bit generator (PRBG) is said to pass
 *    the <em>next-bit test</em> if there is no polynomial-time algorithm which,
 *    on input of the first <code>L</code> bits of an output sequence <code>S</code>,
 *    can predict the <code>(L+1)</code>st bit of <code>S</code> with a
 *    probability significantly grater than <code>1/2</code>."</li>
 *
 *    <li>"5.8 Definition: A PRBG that passes the <em>next-bit test</em>
 *    (possibly under some plausible but unproved mathematical assumption such
 *    as the intractability of factoring integers) is called a
 *    <em>cryptographically secure pseudorandom bit generator</em> (CSPRBG)."</li>
 * </ul>
 *
 * <p><b>IMPLEMENTATION NOTE</b>: Although all the concrete classes in this
 * package implement the {@link Cloneable} interface, it is important to note
 * here that such an operation, for those algorithms that use an underlting
 * symmetric key block cipher, <b>DOES NOT</b> clone any session key material
 * that may have been used in initialising the source PRNG (the instance to be
 * cloned). Instead a clone of an already initialised PRNG, that uses and
 * underlying symmetric key block cipher, is another instance with a clone of
 * the same cipher that operates with the <b>same block size</b> but without any
 * knowledge of neither key material nor key size.</p>
 *
 * <p>References:</p>
 *
 * <ol>
 *    <li><a href="http://www.cacr.math.uwaterloo.ca/hac">[HAC]</a>: Handbook of
 *    Applied Cryptography.<br>
 *    CRC Press, Inc. ISBN 0-8493-8523-7, 1997<br>
 *    Menezes, A., van Oorschot, P. and S. Vanstone.</li>
 * </ol>
 */
public interface IRandom extends Cloneable
{

  // Constants
  // -------------------------------------------------------------------------

  // Methods
  // -------------------------------------------------------------------------

  /**
   * <p>Returns the canonical name of this instance.</p>
   *
   * @return the canonical name of this instance. */
  String name();

  /**
   * <p>Initialises the pseudo-random number generator scheme with the
   * appropriate attributes.</p>
   *
   * @param attributes a set of name-value pairs that describe the desired
   * future instance behaviour.
   * @exception IllegalArgumentException if at least one of the defined name/
   * value pairs contains invalid data.
   */
  void init(Map attributes);

  /**
   * <p>Returns the next 8 bits of random data generated from this instance.</p>
   *
   * @return the next 8 bits of random data generated from this instance.
   * @exception IllegalStateException if the instance is not yet initialised.
   * @exception LimitReachedException if this instance has reached its
   * theoretical limit for generating non-repetitive pseudo-random data.
   */
  byte nextByte() throws IllegalStateException, LimitReachedException;

  /**
   * <p>Fills the designated byte array, starting from byte at index
   * <code>offset</code>, for a maximum of <code>length</code> bytes with the
   * output of this generator instance.
   *
   * @param out the placeholder to contain the generated random bytes.
   * @param offset the starting index in <i>out</i> to consider. This method
   * does nothing if this parameter is not within <code>0</code> and
   * <code>out.length</code>.
   * @param length the maximum number of required random bytes. This method
   * does nothing if this parameter is less than <code>1</code>.
   * @exception IllegalStateException if the instance is not yet initialised.
   * @exception LimitReachedException if this instance has reached its
   * theoretical limit for generating non-repetitive pseudo-random data.
   */
  void nextBytes(byte[] out, int offset, int length)
      throws IllegalStateException, LimitReachedException;

  /**
   * <p>Supplement, or possibly replace, the random state of this PRNG with
   * a random byte.</p>
   *
   * <p>Implementations are not required to implement this method in any
   * meaningful way; this may be a no-operation, and implementations may
   * throw an {@link UnsupportedOperationException}.</p>
   *
   * @param b The byte to add.
   */
  void addRandomByte(byte b);

  /**
   * <p>Supplement, or possibly replace, the random state of this PRNG with
   * a sequence of new random bytes.</p>
   *
   * <p>Implementations are not required to implement this method in any
   * meaningful way; this may be a no-operation, and implementations may
   * throw an {@link UnsupportedOperationException}.</p>
   *
   * @param in The buffer of new random bytes to add.
   */
  void addRandomBytes(byte[] in);

  /**
   * <p>Supplement, or possibly replace, the random state of this PRNG with
   * a sequence of new random bytes.</p>
   *
   * <p>Implementations are not required to implement this method in any
   * meaningful way; this may be a no-operation, and implementations may
   * throw an {@link UnsupportedOperationException}.</p>
   *
   * @param in The buffer of new random bytes to add.
   * @param offset The offset from whence to begin reading random bytes.
   * @param length The number of random bytes to add.
   * @exception IndexOutOfBoundsException If <i>offset</i>, <i>length</i>,
   * or <i>offset</i>+<i>length</i> is out of bounds.
   */
  void addRandomBytes(byte[] in, int offset, int length);

  /**
   * <p>Returns a clone copy of this instance.</p>
   *
   * @return a clone copy of this instance.
   */
  Object clone() throws CloneNotSupportedException;
}