onetimepad.js

/**
 * Simulation of a one-time pad in javascript
 *
 * Key generation done using Math.random, which is seeded with current time
 * Hence, key generation is not actually uniformly random
 **/ 

var OneTimePad = {
	
	// Generate a key of given length using Math.random
	gen: function(length) {
		
		var key = "";
		
		for(var i=0;i<length;i++) {
			key = key.concat(String.fromCharCode(Math.floor(Math.random()*26) + 65));
		}
		
		return key;
	},
	
	// Encrypt a message by xoring it with the key
	enc: function(key, message) {
		
		if(key.length != message.length) return false;
		
		message = message.toUpperCase();
		key = key.toUpperCase();
		
		var cipher = "";
		for(var i=0;i<message.length;i++) {
		
			// XOR each character together and build cipher
			var code = ((key.charCodeAt(i)-65) ^ (message.charCodeAt(i)-65)) + 65;
			cipher = cipher.concat(String.fromCharCode(code));
			
		}
		return cipher;
	
	},
	
	// Note that encryption and decryption are the exact same routine
	dec: function(key, cipher) {
		this.enc(key, cipher);
	}


};

// Bind button to this
function generate() {

	var msg = document.getElementById("message").value;
	document.getElementById("message").value = msg.toUpperCase();
	
	var key = document.getElementById("key").value;
	
	// If the key length is not the same as the message, re-generate the key
	if(msg.length != key.length) {
		key = OneTimePad.gen(msg.length);
		document.getElementById("key").value = key;
	}
	
	var cipher = OneTimePad.enc(key, msg);
	
	if(cipher) {
		document.getElementById("cipher").innerHTML = cipher;
	}

}