Monthly Archives: February 2009

Crackable String Encoding

By Zevan | February 8, 2009
CLICK HERE TO COPY
Actionscript:
  1. var encode:Object = new Object();
  2. var decode:Object = new Object();
  3. var a:Array = " abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".split("");
  4.  
  5. // change this for different encoded results
  6. var offset:int = 10;
  7.  
  8. for (var i:int = 0; i<a.length; i++){
  9.     var index:int = (a.length - i - offset) % a.length;
  10.     encode[a[i]] = a[index];
  11.     decode[a[index]] = a[i];
  12. }
  13.  
  14. function encodeString(str:String):String{
  15.     return map(str, encode);
  16. }
  17.  
  18. function decodeString(str:String):String{
  19.     return map(str, decode);
  20. }
  21.  
  22. function map(str:String, smode:Object):String{
  23.     var n:String = "";
  24.     for (var i:int = 0; i<str.length; i++){
  25.         var char:String = str.charAt(i);
  26.         var en:String = smode[char];
  27.         if (en){
  28.             n += en;
  29.         }else{
  30.             n += char;
  31.         }
  32.     }
  33.     return n;
  34. }
  35.  
  36. // test out the functions
  37.  
  38. var input:String = "This is a regular string";
  39.  
  40. trace(input);
  41.  
  42. var encoded:String = encodeString(input);
  43.  
  44. trace("encoded: ", encoded);
  45.  
  46. trace("decoded: ",decodeString(encoded));
  47.  
  48. /*
  49. outputs:
  50.  
  51. This is a regular string
  52. encoded:  gSRH1RH1Z1IVTFOZI1HGIRMT
  53. decoded:  This is a regular string
  54.  
  55. */

The above demos an intentionally simple string encoding technique.

This is a technique I use if I need to encode strings but don't care if someone figures out what the string value actually is. For me, this is more common than needing hard/impossible to crack string encoding algorithms. A good example is an e-card... a url for an ecard could look like this:

www.birthdaycardthing.com/?name=joe&age=32

or it could look like this:

www.birthdaycardthing.com/?i=brx&x=5p

I wrapped this snippet up into a class and made a few minor tweaks. The class is called SimpleCipher it has two static methods and one static property...

CLICK HERE TO COPY
Actionscript:
  1. import com.actionsnippet.utils.SimpleCipher;
  2. // same as offset above, but can be set at any time
  3. // new encode and decode Objects will be calculated
  4. SimpleCipher.offset = 1;
  5. var input:String = "SimpleCipher encoding and decoding";
  6.              
  7. trace("input: ", input);
  8.              
  9. var encoded:String = SimpleCipher.encode(input);
  10.              
  11. trace("encoded: ", encoded);
  12. trace("decoded: ", SimpleCipher.decode(encoded));
  13. /*
  14. outputs:
  15. input:  SimpleCipher encoding and decoding
  16. encoded:  RhlokdBhogdq0dmbnchmf0 mc0cdbnchmf
  17. decoded:  SimpleCipher encoding and decoding
  18. */

Download SimpleCipher Class
(this class uses a static initializer... see yesterdays post)

Posted in OOP, strings | Tagged , | Leave a comment

Static Constructor / Initializer

By Zevan | February 7, 2009
CLICK HERE TO COPY
Actionscript:
  1. package{
  2.    
  3.     public class Lookup{
  4.        
  5.         private static var _random:Array;
  6.         // static initializer
  7.         {
  8.             trace("I am a static initializer for " + Lookup);
  9.             init();
  10.         }
  11.        
  12.         private static function init():void{
  13.              _random = new Array();
  14.              // generate some filler values
  15.              for (var i:int = 0; i<100; i++){
  16.                 _random.push(Math.random() * i);
  17.              }
  18.         }
  19.        
  20.         public static function get random():Array{
  21.             return _random.concat();
  22.         }
  23.     }
  24. }

...and to test out the above class:

CLICK HERE TO COPY
Actionscript:
  1. package {
  2.     import flash.display.Sprite;
  3.  
  4.     public class Main extends Sprite{
  5.         public function Main(){
  6.            trace(Lookup.random[50]);
  7.         }
  8.     }
  9. }
  10. /*
  11. outputs:
  12. I am a static initializer for [class Lookup]
  13. 5.4258062043227255
  14. */

The above shows how to use static initializers. I've found this to be very handy... in this case we create an array of random values....

Tomorrow I'll actually post a real class where I make use of this... the Lookup class in this case is really just filler code....

Posted in OOP | Tagged , | 1 Comment

Graphics Class Methods in XML

By Zevan | February 6, 2009
CLICK HERE TO COPY
Actionscript:
  1. // for simplicity I left this XML inline, this will work exactly the same if it were external
  2. var program:XML=<body>
  3.                 <draw>
  4.                   <![CDATA[
  5.                    beginFill(0xFF0000);
  6.                    drawCircle(100,100,50);
  7.                    endFill();
  8.                    lineStyle(0, 0x666666);
  9.                    moveTo(100, 100);
  10.                    lineTo(200, 200);
  11.                    moveTo(300, 200);
  12.                    curveTo(350, 300, 400, 200);
  13.                    lineStyle(0, 0x0000FF);
  14.                    drawRect(200, 50,100,100) ;
  15.                     ]]>
  16.                 </draw>
  17. </body>;
  18.  
  19. // parse and run the Graphics class commands from the XML
  20. render(parseFunctions(program.draw.toString()));
  21.  
  22. function parseFunctions(dat:String):Array{
  23.     var a:Array = dat.split(";") ;
  24.     for (var i:int = 0; i<a.length-1; i++){
  25.         a[i] = a[i].split(/\(\)|\(|\)/g);
  26.         var f:String = a[i][0] = a[i][0].replace(/\s/g,"");
  27.         a[i] = a[i].splice(0, a[i].length - 1);
  28.         if (a[i].length> 1){
  29.          a[i] = a[i][1].split(",");
  30.          a[i].unshift(f);
  31.         }
  32.     }
  33.     return a.splice(0,a.length - 1);
  34. }
  35. function render(p:Array):void {
  36.     for (var i:int = 0; i<p.length; i++) {
  37.         graphics[p[i][0]].apply(graphics,p[i].splice(1));
  38.     }
  39. }

The above code builds on yesterdays post by showing how one could potentially store graphics class method calls in XML using a few regular expressions and Function.apply().

The parseFunctions() function reads through the CDATA string and formats it in a 2D array that looks like this:

CLICK HERE TO COPY
Actionscript:
  1. [[beginFill, 0xFF0000], [drawCircle, 100, 100, 50], etc...]

The render() function reads through this 2D array, using the first value of each nested array as the function and the remaining values as arguments...

As is this won't really work with most of the new fp10 graphics methods...

Posted in Graphics, XML, dynamic, external data, functions, string manipulation, strings | Tagged , | Leave a comment

Dynamic Graphics and Function.apply()

By Zevan | February 5, 2009
CLICK HERE TO COPY
Actionscript:
  1. var cmds:Array = [["lineStyle", 0, 0xFF0000], ["drawCircle",100, 100, 50], ["drawRect", 50, 50, 100, 100]];
  2. cmds.push(["drawCircle", 100, 100, 70]);
  3. cmds.push(["beginFill",  0x555555]);
  4. cmds.push(["drawRoundRect", 80, 80, 40, 40, 10, 10]);
  5. cmds.push(["endFill"]);
  6.  
  7. render(cmds);
  8.  
  9. function render(p:Array):void {
  10.     for (var i:int = 0; i<p.length; i++) {
  11.         graphics[p[i][0]].apply(graphics,p[i].splice(1));
  12.     }
  13. }

The above creates a function called render() that takes a 2D array of Graphics class methods and then runs them. This is a very interesting technique, specifically if you'd like to write Graphics class method calls in an XML or txt file and then have them run on a given DisplayObject in flash.

I've been thinking about the best way to do this for awhile... I started off doing something very convoluted and then realized that I could use Function.apply()....

Tomorrow I'll post a snippet showing how to use this function in conjunction with XML.

Posted in Graphics, dynamic, functions | Tagged , | 2 Comments