package gnu.crypto.assembly;

// ----------------------------------------------------------------------------
// $Id: $
//
// Copyright (C) 2003, Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
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// General Public License for more details.
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// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
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// ----------------------------------------------------------------------------

import java.security.InvalidKeyException;

/**
 * <p>The visible methods of every <i>Stage</i> in a Cascade Cipher.</p>
 *
 * <p>Each stage may be either an implementation of a Block Cipher Mode of
 * Operation (address@hidden gnu.crypto.mode.IMode}) or a Cascade Cipher (address@hidden
 * Cascade}). Each stage has also a <i>natural</i> state (operational direction)
 * when constructed for inclusion within a address@hidden Cascade}. This <i>natural</i>
 * state dictates how data flows from one stage into another when they are
 * chained ogether. One can think of a stage and its state as the specification
 * of how to wire the stage to the chain. The following diagrams may help
 * understand the paradigme. The first shows two stages chained together, each
 * with a address@hidden State#FORWARD} state.</p>
 * <pre>
 *           FORWARD         FORWARD
 *       +------+       +-------+
 *       |      |       |       |
 *       |  +--in --+   |   +--in --+
 *    ---+  | Stage |   |   | Stage |  +---
 *          +--out--+   |   +--out--+  |
 *              |       |       |      |
 *              +-------+       +------+
 * </pre>
 * <p>The second diagram shows two stages chained together, the first with a
 * address@hidden State#FORWARD} state, while the second is wired in a address@hidden
 * State#BACKWARD} state.</p>
 * <pre>
 *           FORWARD        BACKWARD
 *       +------+               +------+
 *       |      |               |      |
 *       |  +--in --+       +--in --+  |
 *    ---+  | Stage |       | Stage |  +---
 *          +--out--+       +--out--+
 *              |               |
 *              +---------------+
 * </pre>
 *
 * @see Stage
 * @see ModeStage
 * @see CascadeStage
 * @version $Revision: $
 */
public interface IStage extends Cloneable {

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

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

   /**
    * Initialises the stage for the designated operation.
    *
    * @param state the state to initialise the stage for.
    * @exception IllegalStateException if the instance is not initialised.
    * @throws InvalidKeyException
    * @see State#FORWARD
    * @see State#BACKWARD
    */
   void init(State state) throws InvalidKeyException;

   /**
    * Returns the currently set block size for the stage.
    *
    * @return the current block size for this stage.
    * @exception IllegalStateException if the instance is not initialised.
    */
   int currentBlockSize() throws IllegalStateException;

   /**
    * Resets the stage for re-initialisation and use with other characteristics.
    * This method always succeeds.
    */
   void reset();

   /**
    * Processes exactly one block of <i>plaintext</i> (if initialised in the
    * address@hidden State#FORWARD} state) or <i>ciphertext</i> (if initialised in the
    * address@hidden State#BACKWARD} state).
    *
    * @param in the plaintext.
    * @param inOffset index of <code>in</code> from which to start considering
    * data.
    * @param out the ciphertext.
    * @param outOffset index of <code>out</code> from which to store result.
    * @exception IllegalStateException if the instance is not initialised.
    */
   void update(byte[] in, int inOffset, byte[] out, int outOffset);

   /**
    * Conducts a simple <i>correctness</i> test that consists of basic symmetric
    * encryption / decryption test(s) for all supported block and key sizes of
    * underlying block cipher(s) wrapped by Mode leafs. The test also includes
    * one (1) variable key Known Answer Test (KAT) for each block cipher.
    *
    * @return <code>true</code> if the implementation passes simple
    * <i>correctness</i> tests. Returns <code>false</code> otherwise.
    */
   boolean selfTest();

   /**
    * Returns a clone of this instance.
    *
    * @return a clone copy of this instance.
    */
   Object clone();
}