/js/lib/Socket.IO-node/support/socket.io-client/lib/vendor/web-socket-js/flash-src/com/hurlant/crypto/symmetric/XTeaKey.as

/**

 * XTeaKey

 * 

 * An ActionScript 3 implementation of the XTea algorithm

 * Copyright (c) 2007 Henri Torgemane

 * 

 * See LICENSE.txt for full license information.

 */

package com.hurlant.crypto.symmetric

{

	import com.hurlant.crypto.prng.Random;

	import com.hurlant.util.Memory;

	

	import flash.utils.ByteArray;

	

	

	public class XTeaKey implements ISymmetricKey

	{

		public const NUM_ROUNDS:uint = 64;	

		private var k:Array;



		public function XTeaKey(a:ByteArray) {

			a.position=0;

			k = [a.readUnsignedInt(),a.readUnsignedInt(),a.readUnsignedInt(),a.readUnsignedInt()];

		}

		/**

		 * K is an hex string with 32 digits.

		 */

		public static function parseKey(K:String):XTeaKey {

			var a:ByteArray = new ByteArray;

			a.writeUnsignedInt(parseInt(K.substr(0,8),16));

			a.writeUnsignedInt(parseInt(K.substr(8,8),16));

			a.writeUnsignedInt(parseInt(K.substr(16,8),16));

			a.writeUnsignedInt(parseInt(K.substr(24,8),16));

			a.position = 0;

			return new XTeaKey(a);

		}

		

		public function getBlockSize():uint {

			return 8;

		}



		public function encrypt(block:ByteArray, index:uint=0):void {

			block.position = index;

			var v0:uint = block.readUnsignedInt();

			var v1:uint = block.readUnsignedInt();

			var i:uint;

			var sum:uint =0;

			var delta:uint = 0x9E3779B9;

			for (i=0; i<NUM_ROUNDS; i++) {

				v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + k[sum & 3]);

				sum += delta;

		        v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + k[(sum>>11) & 3]);

			}

			block.position-=8;

			block.writeUnsignedInt(v0);

			block.writeUnsignedInt(v1);

		}

		

		public function decrypt(block:ByteArray, index:uint=0):void {

			block.position = index;

			var v0:uint = block.readUnsignedInt();

			var v1:uint = block.readUnsignedInt();

			var i:uint;

			var delta:uint = 0x9E3779B9;

			var sum:uint = delta*NUM_ROUNDS;

			for (i=0; i<NUM_ROUNDS; i++) {

				v1 -= (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + k[(sum>>11) & 3]);

				sum -= delta;

				v0 -= (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + k[sum & 3]);

			}

			block.position-=8;

			block.writeUnsignedInt(v0);

			block.writeUnsignedInt(v1);

		}



		public function dispose():void {

			//private var k:Array;

			var r:Random = new Random;

			for (var i:uint=0;i<k.length;i++) {

				k[i] = r.nextByte();

				delete k[i];

			}

			k = null;

			Memory.gc();

		}



		public function toString():String {

			return "xtea";

		}

	}

	



}