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package com.sun.crypto.provider;

import java.security.InvalidKeyException;
import javax.crypto.IllegalBlockSizeException;


This class represents a block cipher in one of its modes. It wraps
a SymmetricCipher maintaining the mode state and providing
the capability to encrypt amounts of data larger than a single block.

Author:Jan Luehe
See Also:
/**
 * This class represents a block cipher in one of its modes. It wraps
 * a SymmetricCipher maintaining the mode state and providing
 * the capability to encrypt amounts of data larger than a single block.
 *
 * @author Jan Luehe
 * @see ElectronicCodeBook
 * @see CipherBlockChaining
 * @see CipherFeedback
 * @see OutputFeedback
 * @see PCBC
 */
abstract class FeedbackCipher {

    // the embedded block cipher
    final SymmetricCipher embeddedCipher;

    // the block size of the embedded block cipher
    final int blockSize;

    // the initialization vector
    byte[] iv;

    FeedbackCipher(SymmetricCipher embeddedCipher) {
        this.embeddedCipher = embeddedCipher;
        blockSize = embeddedCipher.getBlockSize();
    }

    final SymmetricCipher getEmbeddedCipher() {
        return embeddedCipher;
    }

    
Gets the block size of the embedded cipher.

Returns:the block size of the embedded cipher
/**
     * Gets the block size of the embedded cipher.
     *
     * @return the block size of the embedded cipher
     */
    final int getBlockSize() {
        return blockSize;
    }

    
Gets the name of the feedback mechanism

Returns:the name of the feedback mechanism
/**
     * Gets the name of the feedback mechanism
     *
     * @return the name of the feedback mechanism
     */
    abstract String getFeedback();

    
Save the current content of this cipher.

/**
     * Save the current content of this cipher.
     */
    abstract void save();

    
Restores the content of this cipher to the previous saved one.

/**
     * Restores the content of this cipher to the previous saved one.
     */
    abstract void restore();

    
Initializes the cipher in the specified mode with the given key
and iv.

Params:
  • decrypting – flag indicating encryption or decryption mode
  • algorithm – the algorithm name (never null)
  • key – the key (never null)
  • iv – the iv (either null or blockSize bytes long)
Throws:
/**
     * Initializes the cipher in the specified mode with the given key
     * and iv.
     *
     * @param decrypting flag indicating encryption or decryption mode
     * @param algorithm the algorithm name (never null)
     * @param key the key (never null)
     * @param iv the iv (either null or blockSize bytes long)
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * initializing this cipher
     */
    abstract void init(boolean decrypting, String algorithm, byte[] key,
                       byte[] iv) throws InvalidKeyException;

   
Gets the initialization vector.

Returns:the initialization vector
/**
     * Gets the initialization vector.
     *
     * @return the initialization vector
     */
    final byte[] getIV() {
        return iv;
    }

    
Resets the iv to its original value.
This is used when doFinal is called in the Cipher class, so that the
cipher can be reused (with its original iv).

/**
     * Resets the iv to its original value.
     * This is used when doFinal is called in the Cipher class, so that the
     * cipher can be reused (with its original iv).
     */
    abstract void reset();

    
Performs encryption operation.

The input plain, starting at plainOffset
and ending at (plainOffset+plainLen-1), is encrypted.
The result is stored in cipher, starting at
cipherOffset.

The subclass that implements Cipher should ensure that
init has been called before this method is called.

Params:
  • plain – the input buffer with the data to be encrypted
  • plainOffset – the offset in plain
  • plainLen – the length of the input data
  • cipher – the buffer for the encryption result
  • cipherOffset – the offset in cipher
/**
     * Performs encryption operation.
     *
     * <p>The input <code>plain</code>, starting at <code>plainOffset</code>
     * and ending at <code>(plainOffset+plainLen-1)</code>, is encrypted.
     * The result is stored in <code>cipher</code>, starting at
     * <code>cipherOffset</code>.
     *
     * <p>The subclass that implements Cipher should ensure that
     * <code>init</code> has been called before this method is called.
     *
     * @param plain the input buffer with the data to be encrypted
     * @param plainOffset the offset in <code>plain</code>
     * @param plainLen the length of the input data
     * @param cipher the buffer for the encryption result
     * @param cipherOffset the offset in <code>cipher</code>
     */
    abstract void encrypt(byte[] plain, int plainOffset, int plainLen,
                          byte[] cipher, int cipherOffset);
    
Performs encryption operation for the last time.

NOTE: For cipher feedback modes which does not perform
special handling for the last few blocks, this is essentially
the same as encrypt(...). Given most modes do
not do special handling, the default impl for this method is
to simply call encrypt(...).

Params:
  • plain – the input buffer with the data to be encrypted
  • plainOffset – the offset in plain
  • plainLen – the length of the input data
  • cipher – the buffer for the encryption result
  • cipherOffset – the offset in cipher
/**
     * Performs encryption operation for the last time.
     *
     * <p>NOTE: For cipher feedback modes which does not perform
     * special handling for the last few blocks, this is essentially
     * the same as <code>encrypt(...)</code>. Given most modes do
     * not do special handling, the default impl for this method is
     * to simply call <code>encrypt(...)</code>.
     *
     * @param plain the input buffer with the data to be encrypted
     * @param plainOffset the offset in <code>plain</code>
     * @param plainLen the length of the input data
     * @param cipher the buffer for the encryption result
     * @param cipherOffset the offset in <code>cipher</code>
     */
     void encryptFinal(byte[] plain, int plainOffset, int plainLen,
                       byte[] cipher, int cipherOffset)
         throws IllegalBlockSizeException {
         encrypt(plain, plainOffset, plainLen, cipher, cipherOffset);
     }
    
Performs decryption operation.

The input cipher, starting at cipherOffset
and ending at (cipherOffset+cipherLen-1), is decrypted.
The result is stored in plain, starting at
plainOffset.

The subclass that implements Cipher should ensure that
init has been called before this method is called.

Params:
  • cipher – the input buffer with the data to be decrypted
  • cipherOffset – the offset in cipher
  • cipherLen – the length of the input data
  • plain – the buffer for the decryption result
  • plainOffset – the offset in plain
/**
     * Performs decryption operation.
     *
     * <p>The input <code>cipher</code>, starting at <code>cipherOffset</code>
     * and ending at <code>(cipherOffset+cipherLen-1)</code>, is decrypted.
     * The result is stored in <code>plain</code>, starting at
     * <code>plainOffset</code>.
     *
     * <p>The subclass that implements Cipher should ensure that
     * <code>init</code> has been called before this method is called.
     *
     * @param cipher the input buffer with the data to be decrypted
     * @param cipherOffset the offset in <code>cipher</code>
     * @param cipherLen the length of the input data
     * @param plain the buffer for the decryption result
     * @param plainOffset the offset in <code>plain</code>
     */
    abstract void decrypt(byte[] cipher, int cipherOffset, int cipherLen,
                          byte[] plain, int plainOffset);

    
Performs decryption operation for the last time.

NOTE: For cipher feedback modes which does not perform
special handling for the last few blocks, this is essentially
the same as encrypt(...). Given most modes do
not do special handling, the default impl for this method is
to simply call decrypt(...).

Params:
  • cipher – the input buffer with the data to be decrypted
  • cipherOffset – the offset in cipher
  • cipherLen – the length of the input data
  • plain – the buffer for the decryption result
  • plainOffset – the offset in plain
/**
     * Performs decryption operation for the last time.
     *
     * <p>NOTE: For cipher feedback modes which does not perform
     * special handling for the last few blocks, this is essentially
     * the same as <code>encrypt(...)</code>. Given most modes do
     * not do special handling, the default impl for this method is
     * to simply call <code>decrypt(...)</code>.
     *
     * @param cipher the input buffer with the data to be decrypted
     * @param cipherOffset the offset in <code>cipher</code>
     * @param cipherLen the length of the input data
     * @param plain the buffer for the decryption result
     * @param plainOffset the offset in <code>plain</code>
     */
     void decryptFinal(byte[] cipher, int cipherOffset, int cipherLen,
                       byte[] plain, int plainOffset)
         throws IllegalBlockSizeException {
         decrypt(cipher, cipherOffset, cipherLen, plain, plainOffset);
     }
}