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	/*
	* Copyright (c) 2003, 2017, 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.*;
	import java.security.spec.AlgorithmParameterSpec;

	import javax.crypto.*;

	/**
	* Implementation of the ARCFOUR cipher, an algorithm apparently compatible
	* with RSA Security's RC4(tm) cipher. The description of this algorithm was
	* taken from Bruce Schneier's book Applied Cryptography, 2nd ed.,
	* section 17.1.
	*
	* We support keys from 40 to 1024 bits. ARCFOUR would allow for keys shorter
	* than 40 bits, but that is too insecure for us to permit.
	*
	* Note that we subclass CipherSpi directly and do not use the CipherCore
	* framework. That was designed to simplify implementation of block ciphers
	* and does not offer any advantages for stream ciphers such as ARCFOUR.
	*
	* @since 1.5
	* @author Andreas Sterbenz
	*/
	public final class ARCFOURCipher extends CipherSpi {

	// state array S, 256 entries. The entries are 8-bit, but we use an int[]
	// because int arithmetic is much faster than in Java than bytes.
	private final int[] S;

	// state indices i and j. Called is and js to avoid collision with
	// local variables. 'is' is set to -1 after a call to doFinal()
	private int is, js;

	// the bytes of the last key used (if any)
	// we need this to re-initialize after a call to doFinal()
	private byte[] lastKey;

	// called by the JCE framework
	public ARCFOURCipher() {
	S = new int[256];
	}

	// core key setup code. initializes S, is, and js
	// assumes key is non-null and between 40 and 1024 bit
	private void init(byte[] key) {
	// initialize S[i] to i
	for (int i = 0; i < 256; i++) {
	S[i] = i;
	}

	// we avoid expanding key to 256 bytes and instead keep a separate
	// counter ki = i mod key.length.
	for (int i = 0, j = 0, ki = 0; i < 256; i++) {
	int Si = S[i];
	j = (j + Si + key[ki]) & 0xff;
	S[i] = S[j];
	S[j] = Si;
	ki++;
	if (ki == key.length) {
	ki = 0;
	}
	}

	// set indices to 0
	is = 0;
	js = 0;
	}

	// core crypt code. OFB style, so works for both encryption and decryption
	private void crypt(byte[] in, int inOfs, int inLen, byte[] out,
	int outOfs) {
	if (is < 0) {
	// doFinal() was called, need to reset the cipher to initial state
	init(lastKey);
	}
	while (inLen-- > 0) {
	is = (is + 1) & 0xff;
	int Si = S[is];
	js = (js + Si) & 0xff;
	int Sj = S[js];
	S[is] = Sj;
	S[js] = Si;
	out[outOfs++] = (byte)(in[inOfs++] ^ S[(Si + Sj) & 0xff]);
	}
	}

	// Modes do not make sense with stream ciphers, but allow ECB
	// see JCE spec.
	protected void engineSetMode(String mode) throws NoSuchAlgorithmException {
	if (mode.equalsIgnoreCase("ECB") == false) {
	throw new NoSuchAlgorithmException("Unsupported mode " + mode);
	}
	}

	// Padding does not make sense with stream ciphers, but allow NoPadding
	// see JCE spec.
	protected void engineSetPadding(String padding)
	throws NoSuchPaddingException {
	if (padding.equalsIgnoreCase("NoPadding") == false) {
	throw new NoSuchPaddingException("Padding must be NoPadding");
	}
	}

	// Return 0 to indicate stream cipher
	// see JCE spec.
	protected int engineGetBlockSize() {
	return 0;
	}

	// output length is always the same as input length
	// see JCE spec
	protected int engineGetOutputSize(int inputLen) {
	return inputLen;
	}

	// no IV, return null
	// see JCE spec
	protected byte[] engineGetIV() {
	return null;
	}

	// no parameters
	// see JCE spec
	protected AlgorithmParameters engineGetParameters() {
	return null;
	}

	// see JCE spec
	protected void engineInit(int opmode, Key key, SecureRandom random)
	throws InvalidKeyException {
	init(opmode, key);
	}

	// see JCE spec
	protected void engineInit(int opmode, Key key,
	AlgorithmParameterSpec params, SecureRandom random)
	throws InvalidKeyException, InvalidAlgorithmParameterException {
	if (params != null) {
	throw new InvalidAlgorithmParameterException
	("Parameters not supported");
	}
	init(opmode, key);
	}

	// see JCE spec
	protected void engineInit(int opmode, Key key,
	AlgorithmParameters params, SecureRandom random)
	throws InvalidKeyException, InvalidAlgorithmParameterException {
	if (params != null) {
	throw new InvalidAlgorithmParameterException
	("Parameters not supported");
	}
	init(opmode, key);
	}

	// init method. Check opmode and key, then call init(byte[]).
	private void init(int opmode, Key key) throws InvalidKeyException {
	if ((opmode < Cipher.ENCRYPT_MODE) \|\| (opmode > Cipher.UNWRAP_MODE)) {
	throw new InvalidKeyException("Unknown opmode: " + opmode);
	}
	lastKey = getEncodedKey(key);
	init(lastKey);
	}

	// return the encoding of key if key is a valid ARCFOUR key.
	// otherwise, throw an InvalidKeyException
	private static byte[] getEncodedKey(Key key) throws InvalidKeyException {
	String keyAlg = key.getAlgorithm();
	if (!keyAlg.equals("RC4") && !keyAlg.equals("ARCFOUR")) {
	throw new InvalidKeyException("Not an ARCFOUR key: " + keyAlg);
	}
	if ("RAW".equals(key.getFormat()) == false) {
	throw new InvalidKeyException("Key encoding format must be RAW");
	}
	byte[] encodedKey = key.getEncoded();
	if ((encodedKey.length < 5) \|\| (encodedKey.length > 128)) {
	throw new InvalidKeyException
	("Key length must be between 40 and 1024 bit");
	}
	return encodedKey;
	}

	// see JCE spec
	protected byte[] engineUpdate(byte[] in, int inOfs, int inLen) {
	byte[] out = new byte[inLen];
	crypt(in, inOfs, inLen, out, 0);
	return out;
	}

	// see JCE spec
	protected int engineUpdate(byte[] in, int inOfs, int inLen,
	byte[] out, int outOfs) throws ShortBufferException {
	if (out.length - outOfs < inLen) {
	throw new ShortBufferException("Output buffer too small");
	}
	crypt(in, inOfs, inLen, out, outOfs);
	return inLen;
	}

	// see JCE spec
	protected byte[] engineDoFinal(byte[] in, int inOfs, int inLen) {
	byte[] out = engineUpdate(in, inOfs, inLen);
	is = -1;
	return out;
	}

	// see JCE spec
	protected int engineDoFinal(byte[] in, int inOfs, int inLen,
	byte[] out, int outOfs) throws ShortBufferException {
	int outLen = engineUpdate(in, inOfs, inLen, out, outOfs);
	is = -1;
	return outLen;
	}

	// see JCE spec
	protected byte[] engineWrap(Key key) throws IllegalBlockSizeException,
	InvalidKeyException {
	byte[] encoded = key.getEncoded();
	if ((encoded == null) \|\| (encoded.length == 0)) {
	throw new InvalidKeyException("Could not obtain encoded key");
	}
	return engineDoFinal(encoded, 0, encoded.length);
	}

	// see JCE spec
	protected Key engineUnwrap(byte[] wrappedKey, String algorithm,
	int type) throws InvalidKeyException, NoSuchAlgorithmException {
	byte[] encoded = engineDoFinal(wrappedKey, 0, wrappedKey.length);
	return ConstructKeys.constructKey(encoded, algorithm, type);
	}

	// see JCE spec
	protected int engineGetKeySize(Key key) throws InvalidKeyException {
	byte[] encodedKey = getEncodedKey(key);
	return Math.multiplyExact(encodedKey.length, 8);
	}

	}

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