Simple Encryption and Decryption

Monoalphabetical Substitution Cipher in Flex Monoalphabetic Substitution Cipher is a encryption algorithm which was used in old times. In this algorithm each letter is replaced with another letter according to the cipher alphabet based on the key word.
Look at the following example:
key word: leila
PlainText Alphabet: abcdefghijklmnopqrstuvwxyz
CipherText Alphabet: leiabcdfghjkmnopqrstuvwxyz
Following is the ActionScript code for the ciphering by monoalphabetic algorithm.
import mx.collections.ArrayCollection; private var key:String; private var plainText:Array ; private var txtPlainWord:ArrayCollection = new ArrayCollection(); private var arrSplit:Array = new Array(); private var arrText:Array = new Array('a', 'b', 'c', 'd', 'e','f','g','h', 'i','j','k','l','m','n','o','p','q','r', 's','t','u','v','w','x','y','z'); /* get_key function is for omitting the repeated letters of the Key and find equal plain and cipher letter*/ private function get_key():void { var flag:Boolean = false; key = txtKey.text.toLowerCase(); plainText = new Array() txtPlainWord.removeAll(); //omitting the repeated letters of the Key for (var i:int= 0; i<= key.length-1 ; i++ ) { if (i == 0) plainText.push(key.charAt(0)); else { for (var idx:int = 0; idx<= plainText.length -1 ; idx++) { if (plainText[idx].toString() == key.charAt(i).toString()) { flag = true; break; } else flag = false; } if (flag == false) plainText.push(key.charAt(i)); } } // adding modified Key and find equal plain and cipher letter for (var ix:int= 0; ix<= arrText.length-1 ; ix++ ) { for (var J:int = 0; J<= plainText.length -1 ; J++) { if (plainText[J].toString() == arrText[ix].toString()) { flag = true; break; } else flag = false; } if (flag == false) plainText.push(arrText[ix]); } for (var obj:int; obj<= arrText.length - 1 ; obj++) { var obj1:Object = new Object(); obj1.plain = arrText[obj]; obj1.cipher = plainText[obj]; txtPlainWord.addItem(obj1) } } private function do_decrypt():void { get_key(); txtPlainText.text = txtPlainText.text.toLowerCase(); arrSplit = txtPlainText.text.split(' '); for (var i:int= 0; i<= arrSplit.length-1 ; i++ ) { var txtSplit:String = arrSplit[i]; for (var obj:int= 0; obj<= txtSplit.length-1 ; obj++ ) { for (var idx:int = 0 ; idx<= txtPlainWord.length-1; idx++) { if (txtPlainWord.getItemAt(idx).plain == txtSplit.charAt(obj)) txtCipherText.text = txtCipherText.text + txtPlainWord.getItemAt(idx).cipher; } } txtCipherText.text = txtCipherText.text + " "; } } private function do_encrypt():void { get_key(); txtCipherText.text = txtCipherText.text.toLowerCase(); arrSplit = txtCipherText.text.split(' '); for (var i:int= 0; i<= arrSplit.length-1 ; i++ ) { var txtSplit:String = arrSplit[i]; for (var obj:int= 0; obj<= txtSplit.length-1 ; obj++ ) { for (var idx:int = 0 ; idx<= txtPlainWord.length-1; idx++) { if (txtPlainWord.getItemAt(idx).cipher == txtSplit.charAt(obj)) txtPlainText.text = txtPlainText.text + txtPlainWord.getItemAt(idx).plain; } } txtPlainText.text = txtPlainText.text + " "; } }
Following is the monoalphabetic cipher MXML codes in Flex.
<mx:Canvas width="500" height="203" borderStyle="inset"> <mx:HBox x="10" y="10" height="25" > <mx:Label text="Key:" height="100%" width="100" fontSize="11"/> <mx:TextInput id="txtKey" height="100%" width="100%"/> </mx:HBox> <mx:HBox x="10" y="35" width="400"> <mx:Label text="Plain Text:" height="100%" width="100" fontSize="11"/> <mx:TextInput id="txtPlainText" height="100%" width="100%"/> </mx:HBox> <mx:HBox x="10" y="57" width="400"> <mx:Label text="Cipher Text:" height="100%" width="100" fontSize="11"/> <mx:TextInput id="txtCipherText" height="100%" width="100%"/> </mx:HBox> <mx:Button id= "btnDecrypt" label="Decrypt" click="do_decrypt();"/> <mx:Button id="btnEncrypt" label="Encrypt" click="do_encrypt();"> <mx:Button id="btnReset" label="Clear" click="txtCipherText.text = ''; txtPlainText.text = ''"/> </mx:Canvas>

Following is the screen shot  of monoalphabetic cipher algorithm in flex to show how the codes work.