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source/com/hurlant/crypto/symmetric/XTeaKey.as

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+/**
+ * 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";
+		}
+	}
+	
+
+}