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- /*
- * Copyright (c) 2009 Chris Smith
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
-
- package com.md87.util.crypto;
-
- import java.util.Arrays;
-
- /**
- * Implements the ARC4 algorithm.
- *
- * @author chris
- */
- public class ArcFourEncrypter {
-
- /** The key to use for encryption. */
- final String key;
-
- /** The output of the key scheduling algorithm. */
- final byte[] ostate = new byte[256];
-
- /**
- * Creates a new encrypter that will use the specified key.
- *
- * @param key The key to use for encrypting
- */
- public ArcFourEncrypter(final String key) {
- this.key = key;
-
- byte[] bytes = key.getBytes();
-
- for (int i = 0; i < 256; i++) {
- ostate[i] = (byte) i;
- }
-
- int keyindex = 0;
- int stateindex = 0;
-
- for (int i = 0; i < 256; i++) {
- stateindex = (stateindex + bytes[keyindex] + ostate[i]) & 0xff;
- final byte u = ostate[stateindex];
- ostate[stateindex] = (byte) (ostate[i] & 0xff);
- ostate[i] = (byte) (u & 0xff);
-
- keyindex = (keyindex + 1) % bytes.length;
- }
- }
-
- /**
- * Encrypts the specified bytes.
- *
- * @param bytes The bytes to be encrypted
- * @return The encrypted bytes
- */
- public byte[] encrypt(final byte[] bytes) {
- final byte[] state = Arrays.copyOf(ostate, ostate.length);
- final byte[] dest = new byte[bytes.length];
- int x = 0, y = 0;
-
- for (int i = 0; i < bytes.length; i++) {
- x = (x + 1) & 0xff;
- byte sx = state[x];
- y = (sx + y) & 0xff;
- byte sy = state[y];
-
- state[y] = (byte) (sx & 0xff);
- state[x] = (byte) (sy & 0xff);
-
- dest[i] = (byte) (((int) bytes[i] ^ state[(sx + sy) & 0xff]) & 0xff);
- }
-
- return dest;
- }
-
- }
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