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

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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;
}