Merge pull request #78 from winsonrich/patch-4

Create keyFinder.js

Author: ms10398

Ciphers/keyFinder.js

@@ -0,0 +1,27 @@
+/******************************************************
+Find and retrieve the encryption key automatically 
+Note: This is a draft version, please help to modify, Thanks!
+******************************************************/
+function keyFinder(str){ // str is used to get the input of encrypted string
+	var key = 0; // return zero means the key can not be found
+	var wordbank =["is","Is","am","Am","are","Are","have","Have","has","Has","may","May","be","Be"];
+ 	//var shiftNum = 0; //count the number of key shifted
+	var inStr = str.toString(); //convert the input to String
+	var outStr = ""; // store the output value
+	var wordInOutStr = ""; // temporary store the word inside the outStr, it is used for comparison
+ 	//document.getElementById("debug").innerHTML = shiftNum; // debug: display the shifted number(s) 
+ 	for (var i=0; i<(52); i++){ //try the number of key shifted, the sum of character from a-z and A-Z is 26*2=52
+		outStr = caesarCipherEncodeAndDecodeEngine(inStr,i); // use the encrytpion engine to decrypt the input string, shiftNum=i
+		for ( var i=0; i<wordbank.length; i++){
+			// use a loop to find the next digit of wordbank element and compare with outStr's digit
+			for ( var j=0; j < wordbank[i].length; j++){
+				wordInOutStr += outStr[i+j];
+			}
+			// this part need to be optimize with the calculation of the number of occurance of word's probabilities
+			if (wordbank[i] == wordInOutStr){
+        			key=i;
+			}
+		}
+	}
+	return key;
+}