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/* IRandom.java --

   Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

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it under the terms of the GNU General Public License as published by

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Linking this library statically or dynamically with other modules is

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permission to link this library with independent modules to produce an

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independent module, the terms and conditions of the license of that

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exception statement from your version.  */

package gnu.java.security.prng;

import java.util.Map;

/**

 * The basic visible methods of any pseudo-random number generator.

 * <p>

 * The [HAC] defines a PRNG (as implemented in this library) as follows:

 * <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><sup>st</sup> bit of <code>S</code> with a

 * probability significantly greater 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 underlying

 * 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 an

 * 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>

 * References:

 * <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

{

  /**

   * Returns the canonical name of this instance.

   *

   * @return the canonical name of this instance.

   */

  String name();

  /**

   * Initialises the pseudo-random number generator scheme with the appropriate

   * attributes.

   *

   * @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);

  /**

   * Returns the next 8 bits of random data generated from this instance.

   *

   * @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;

  /**

   * 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;

  /**

   * Supplement, or possibly replace, the random state of this PRNG with a

   * random byte.

   * <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}.

   *

   * @param b The byte to add.

   */

  void addRandomByte(byte b);

  /**

   * Supplement, or possibly replace, the random state of this PRNG with a

   * sequence of new random bytes.

   * <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}.

   *

   * @param in The buffer of new random bytes to add.

   */

  void addRandomBytes(byte[] in);

  /**

   * Supplement, or possibly replace, the random state of this PRNG with a

   * sequence of new random bytes.

   * <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}.

   *

   * @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);

  /**

   * Returns a clone copy of this instance.

   *

   * @return a clone copy of this instance.

   */

  Object clone() throws CloneNotSupportedException;

}