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	/*
	* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package com.sun.crypto.provider;

	import java.security.InvalidKeyException;
	import java.security.ProviderException;

	/**
	* This class represents ciphers in cipher-feedback (CFB) mode.
	*
	* <p>This mode is implemented independently of a particular cipher.
	* Ciphers to which this mode should apply (e.g., DES) must be
	* <i>plugged-in</i> using the constructor.
	*
	* <p>NOTE: This class does not deal with buffering or padding.
	*
	* @author Gigi Ankeny
	*/

	final class CipherFeedback extends FeedbackCipher {

	/*
	* encrypt/decrypt output buffer
	*/
	private final byte[] k;

	/*
	* register value, initialized with iv
	*/
	private final byte[] register;

	/*
	* number of bytes for each stream unit, defaults to the blocksize
	* of the embedded cipher
	*/
	private int numBytes;

	// variables for save/restore calls
	private byte[] registerSave = null;

	CipherFeedback(SymmetricCipher embeddedCipher, int numBytes) {
	super(embeddedCipher);
	if (numBytes > blockSize) {
	numBytes = blockSize;
	}
	this.numBytes = numBytes;
	k = new byte[blockSize];
	register = new byte[blockSize];
	}

	/**
	* Gets the name of this feedback mode.
	*
	* @return the string <code>CFB</code>
	*/
	String getFeedback() {
	return "CFB";
	}

	/**
	* Initializes the cipher in the specified mode with the given key
	* and iv.
	*
	* @param decrypting flag indicating encryption or decryption
	* @param algorithm the algorithm name
	* @param key the key
	* @param iv the iv
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* initializing this cipher
	*/
	void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
	throws InvalidKeyException {
	if ((key == null) \|\| (iv == null) \|\| (iv.length != blockSize)) {
	throw new InvalidKeyException("Internal error");
	}
	this.iv = iv;
	reset();
	// always encrypt mode for embedded cipher
	embeddedCipher.init(false, algorithm, key);
	}

	/**
	* 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).
	*/
	void reset() {
	System.arraycopy(iv, 0, register, 0, blockSize);
	}

	/**
	* Save the current content of this cipher.
	*/
	void save() {
	if (registerSave == null) {
	registerSave = new byte[blockSize];
	}
	System.arraycopy(register, 0, registerSave, 0, blockSize);
	}

	/**
	* Restores the content of this cipher to the previous saved one.
	*/
	void restore() {
	System.arraycopy(registerSave, 0, register, 0, blockSize);
	}

	/**
	* Performs encryption operation.
	*
	* <p>The input plain text <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>.
	*
	* @param plain the buffer with the input 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 result
	* @param cipherOffset the offset in <code>cipher</code>
	* @exception ProviderException if <code>plainLen</code> is not
	* a multiple of the <code>numBytes</code>
	* @return the length of the encrypted data
	*/
	int encrypt(byte[] plain, int plainOffset, int plainLen,
	byte[] cipher, int cipherOffset) {
	if ((plainLen % numBytes) != 0) {
	throw new ProviderException("Internal error in input buffering");
	}

	int nShift = blockSize - numBytes;
	int loopCount = plainLen / numBytes;

	for (; loopCount > 0 ;
	plainOffset += numBytes, cipherOffset += numBytes,
	loopCount--) {
	embeddedCipher.encryptBlock(register, 0, k, 0);
	if (nShift != 0) {
	System.arraycopy(register, numBytes, register, 0, nShift);
	}
	for (int i = 0; i < numBytes; i++) {
	register[nShift + i] = cipher[i + cipherOffset] =
	(byte)(k[i] ^ plain[i + plainOffset]);
	}
	}
	return plainLen;
	}

	/**
	* Performs the last encryption operation.
	*
	* <p>The input plain text <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>.
	*
	* @param plain the buffer with the input 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 result
	* @param cipherOffset the offset in <code>cipher</code>
	* @return the number of bytes placed into <code>cipher</code>
	*/
	int encryptFinal(byte[] plain, int plainOffset, int plainLen,
	byte[] cipher, int cipherOffset) {

	int oddBytes = plainLen % numBytes;
	int len = encrypt(plain, plainOffset, (plainLen - oddBytes),
	cipher, cipherOffset);
	plainOffset += len;
	cipherOffset += len;
	if (oddBytes != 0) {
	embeddedCipher.encryptBlock(register, 0, k, 0);
	for (int i = 0; i < oddBytes; i++) {
	cipher[i + cipherOffset] =
	(byte)(k[i] ^ plain[i + plainOffset]);
	}
	}
	return plainLen;
	}

	/**
	* Performs decryption operation.
	*
	* <p>The input cipher text <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>.
	*
	* @param cipher the buffer with the input data to be decrypted
	* @param cipherOffset the offset in <code>cipherOffset</code>
	* @param cipherLen the length of the input data
	* @param plain the buffer for the result
	* @param plainOffset the offset in <code>plain</code>
	* @exception ProviderException if <code>cipherLen</code> is not
	* a multiple of the <code>numBytes</code>
	* @return the length of the decrypted data
	*/
	int decrypt(byte[] cipher, int cipherOffset, int cipherLen,
	byte[] plain, int plainOffset) {
	if ((cipherLen % numBytes) != 0) {
	throw new ProviderException("Internal error in input buffering");
	}

	int nShift = blockSize - numBytes;
	int loopCount = cipherLen / numBytes;

	for (; loopCount > 0;
	plainOffset += numBytes, cipherOffset += numBytes,
	loopCount--) {
	embeddedCipher.encryptBlock(register, 0, k, 0);
	if (nShift != 0) {
	System.arraycopy(register, numBytes, register, 0, nShift);
	}
	for (int i = 0; i < numBytes; i++) {
	register[i + nShift] = cipher[i + cipherOffset];
	plain[i + plainOffset]
	= (byte)(cipher[i + cipherOffset] ^ k[i]);
	}
	}
	return cipherLen;
	}

	/**
	* Performs the last decryption operation.
	*
	* <p>The input cipher text <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>.
	*
	* @param cipher the buffer with the input data to be decrypted
	* @param cipherOffset the offset in <code>cipherOffset</code>
	* @param cipherLen the length of the input data
	* @param plain the buffer for the result
	* @param plainOffset the offset in <code>plain</code>
	* @return the length of the decrypted data
	*/
	int decryptFinal(byte[] cipher, int cipherOffset, int cipherLen,
	byte[] plain, int plainOffset) {

	int oddBytes = cipherLen % numBytes;
	int len = decrypt(cipher, cipherOffset, (cipherLen - oddBytes),
	plain, plainOffset);
	cipherOffset += len;
	plainOffset += len;
	if (oddBytes != 0) {
	embeddedCipher.encryptBlock(register, 0, k, 0);
	for (int i = 0; i < oddBytes; i++) {
	plain[i + plainOffset]
	= (byte)(cipher[i + cipherOffset] ^ k[i]);
	}
	}
	return cipherLen;
	}
	}

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