[Flash] as3crypto

• as3crypto

as3crypto是由henrit等人合力完成的Actionscript 3.0 Cryptography Library，提供了RSA、Data Encryption、Message-Digest等功能，讓Flash使用者可以輕鬆完成加密的工作，你可以從下面的網頁下載到這個API

http://code.google.com/p/as3crypto/

官方提供了一個很好的範例如下：

http://crypto.hurlant.com/demo/

我則使用as3crypto簡單做了一個Data Encryption/Decryption的demo（理論上來說，如果要為了效能應該是要用C+OpenSSL），程式碼裡直接指定使用Triple-DES+ECB Mode，而Key的長度預設為128bits，原始碼如下：

package{
import flash.display.Sprite;
import flash.net.FileReference;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.utils.ByteArray;

import fl.controls.Button;

import com.hurlant.crypto.symmetric.ICipher;
import com.hurlant.crypto.symmetric.IVMode;
import com.hurlant.crypto.symmetric.IMode;
import com.hurlant.crypto.symmetric.NullPad;
import com.hurlant.crypto.symmetric.PKCS5;
import com.hurlant.crypto.symmetric.IPad;
import com.hurlant.crypto.prng.Random;
import com.hurlant.crypto.hash.HMAC;
import com.hurlant.util.Base64;
import com.hurlant.util.Hex;
import com.hurlant.crypto.Crypto;
import com.hurlant.crypto.hash.IHash;

public class CryptoDemo extends Sprite{
private var loadFile:FileReference;
private var saveFile:FileReference;

private var plainData:ByteArray;
private var cipherData:ByteArray;

private var option:String;

public function CryptoDemo(){
encryBtn.label= "Encrypt";
encryBtn.addEventListener(MouseEvent.CLICK, onClicked);

decryBtn.label = "Decrypt";
decryBtn.addEventListener(MouseEvent.CLICK, onClicked);

keyLabel.text = "Key:";
infoLabel.text = "Info:";

genKeyBtn.label = "Generate 128 Bits";
genKeyBtn.addEventListener(MouseEvent.CLICK, onClicked);

loadFile = new FileReference();
loadFile.addEventListener(Event.SELECT, onFileSelected);
loadFile.addEventListener(Event.COMPLETE, onFileLoaded);

saveFile = new FileReference();
}

private function onClicked(event:MouseEvent):Boolean{
if(event.target.label == "Generate 128 Bits"){
genKey(128);
}else{
if(keyIn.text == ""){
infoTxt.text = "Please give a key!";
return false;
}
option = event.target.label;
loadFile.browse();
}

return true;
}

private function onFileSelected(event:Event):void{
event.target.load();
}

private function onFileLoaded(event:Event):void{
infoTxt.text = "Filename: "+event.target.name+"\nSize: "+event.target.size+" Bytes";

switch(option){
case "Encrypt":
plainData = event.target.data;
encrypt();
saveFile.save(plainData, "encrypt.dat");
break;
case "Decrypt":
cipherData = event.target.data;
decrypt();
saveFile.save(cipherData, "decrypt.dat");
break;
}

plainData = cipherData = null;
}

private function genKey(v:int):void {
var r:Random = new Random;
var b:ByteArray = new ByteArray
r.nextBytes(b, v/8);
keyIn.text = Hex.fromArray(b);
}

private function encrypt():void {
// key
var k:String = keyIn.text;
var kdata:ByteArray;
kdata = Hex.toArray(Hex.fromString(k));

// algorithm..
var name:String = "simple-des3-ecb";

// encryption
var pad:IPad = new PKCS5;
var mode:ICipher = Crypto.getCipher(name, kdata, pad);
pad.setBlockSize(mode.getBlockSize());
mode.encrypt(plainData);
}

private function decrypt():void {
// key
var k:String = keyIn.text;
var kdata:ByteArray;
kdata = Hex.toArray(Hex.fromString(k));

// algorithm..
var name:String = "simple-des3-ecb";

// decryption
var pad:IPad = new PKCS5;
var mode:ICipher = Crypto.getCipher(name, kdata, pad);
pad.setBlockSize(mode.getBlockSize());
mode.decrypt(cipherData);
}
}
}


預覽畫面如下：

由於Flash Player基於安全性的考量，FileReference物件的save()函式必須由mouse click等event來觸發，所以上面的範例將無法讓你正常儲存。