/* IBlockCipher.java -- 
   Copyright (C) 2001, 2002, 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
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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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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.cipher;

import java.security.InvalidKeyException;
import java.util.Iterator;
import java.util.Map;

/**
 * The basic visible methods of any symmetric key block cipher.
 * <p>
 * A symmetric key block cipher is a function that maps n-bit plaintext blocks
 * to n-bit ciphertext blocks; n being the cipher's <i>block size</i>. This
 * encryption function is parameterised by a k-bit key, and is invertible. Its
 * inverse is the decryption function.
 * <p>
 * Possible initialisation values for an instance of this type are:
 * <ul>
 * <li>The block size in which to operate this block cipher instance. This
 * value is <b>optional</b>, if unspecified, the block cipher's default block
 * size shall be used.</li>
 * <li>The byte array containing the user supplied key material to use for
 * generating the cipher's session key(s). This value is <b>mandatory</b> and
 * should be included in the initialisation parameters. If it isn't, an
 * {@link IllegalStateException} will be thrown if any method, other than
 * <code>reset()</code> is invoked on the instance. Furthermore, the size of
 * this key material shall be taken as an indication on the key size in which to
 * operate this instance.</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 <b>DOES NOT</b> clone any session key material
 * that may have been used in initialising the source cipher (the instance to be
 * cloned). Instead a clone of an already initialised cipher is another instance
 * that operates with the <b>same block size</b> but without any knowledge of
 * neither key material nor key size.
 */
public interface IBlockCipher
    extends Cloneable
{
  /**
   * Property name of the block size in which to operate a block cipher. The
   * value associated with this property name is taken to be an {@link Integer}.
   */
  String CIPHER_BLOCK_SIZE = "gnu.crypto.cipher.block.size";
  /**
   * Property name of the user-supplied key material. The value associated to
   * this property name is taken to be a byte array.
   */
  String KEY_MATERIAL = "gnu.crypto.cipher.key.material";

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

  /**
   * Returns the default value, in bytes, of the algorithm's block size.
   * 
   * @return the default value, in bytes, of the algorithm's block size.
   */
  int defaultBlockSize();

  /**
   * Returns the default value, in bytes, of the algorithm's key size.
   * 
   * @return the default value, in bytes, of the algorithm's key size.
   */
  int defaultKeySize();

  /**
   * Returns an {@link Iterator} over the supported block sizes. Each element
   * returned by this object is an {@link Integer}.
   * 
   * @return an {@link Iterator} over the supported block sizes.
   */
  Iterator blockSizes();

  /**
   * Returns an {@link Iterator} over the supported key sizes. Each element
   * returned by this object is an {@link Integer}.
   * 
   * @return an {@link Iterator} over the supported key sizes.
   */
  Iterator keySizes();

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

  /**
   * Initialises the algorithm with designated attributes. Permissible names and
   * values are described in the class documentation above.
   * 
   * @param attributes a set of name-value pairs that describes the desired
   *          future behaviour of this instance.
   * @exception InvalidKeyException if the key data is invalid.
   * @exception IllegalStateException if the instance is already initialised.
   * @see #KEY_MATERIAL
   * @see #CIPHER_BLOCK_SIZE
   */
  void init(Map attributes) throws InvalidKeyException, IllegalStateException;

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

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

  /**
   * Encrypts exactly one block of plaintext.
   * 
   * @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 encryptBlock(byte[] in, int inOffset, byte[] out, int outOffset)
      throws IllegalStateException;

  /**
   * Decrypts exactly one block of ciphertext.
   * 
   * @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 decryptBlock(byte[] in, int inOffset, byte[] out, int outOffset)
      throws IllegalStateException;

  /**
   * A <i>correctness</i> test that consists of basic symmetric encryption /
   * decryption test(s) for all supported block and key sizes, as well as one
   * (1) variable key Known Answer Test (KAT).
   * 
   * @return <code>true</code> if the implementation passes simple
   *         <i>correctness</i> tests. Returns <code>false</code> otherwise.
   */
  boolean selfTest();
}