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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";
}
}
}
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