LFSR.js

var LfsrCipher = function(s, p) {
  this.key = s;
  this.p = p;
  
  this.generate = function(i) {
  	var t = 0;
		for(var j=0; j<=p.length-1; j++) 
			t += p[j] * s[i+j];
		
		t = t % 2;
		s.push(t);
		return t;
  }
  
  this.encrypt = function(message) {
  	this.s = this.key;
  	var cipherText = [];
    
		for(var i=0; i<message.length; i++) {
			cipherText.push(message[i] ^ this.generate(i));
		}
		
		return cipherText;
  }
  
  this.decrypt = function(cipherText) {
  	return this.encrypt(cipherText)
  }
}

var cipher = new LfsrCipher([0, 1, 1, 0, 0], [1, 1, 0, 0, 1]);
var text = cipher.encrypt([1, 1, 1, 0, 0, 0, 1, 0, 1, 0]);
var message = cipher.decrypt(text);