Some functions to understand RSA encryption with *little* numbers

rsaexample.js

findInverse=function(a,b){
	n=b;x=0;lastx=1;
	while (b!= 0){
		q=~~(a/b);
		temp=a;
		a=b;
		b=temp % b;
		temp=x;
		x= lastx - q*temp;
		lastx=temp;
	}
	if (lastx<0) lastx+=n;
	if (a!=1) lastx=0;
	return lastx;
}
function expmodn(a,b,n){
e=a;
for (i=1;i<b;i++) e=e*a % n;
return e;
}
function msgToNumbers(s){
	let a=Array();
	for (i in s) a.push(s.charCodeAt(i));
	return a;
}

function numbersToMsg(a){
	s='';
	for (i in a) s+=String.fromCharCode(a[i]);
	return s;
}




rsakey=function(e, b){
	this.exp=e;
	this.modulo=b;
	this.encryptNumbers=function(a){
		encripted=Array();
		for (i in a) encripted.push(expmodn(a[i], this.exp, this.modulo));
		return encripted;
	}
	this.encrypt=function(s){
		let a=msgToNumbers(s);
		return numbersToMsg(this.encryptNumbers(a));
}
}




msg='ciao mondo';
nmsg=msgToNumbers(msg);
pubkey=new rsakey(9, 253);
pvtkey=new rsakey(49, 253);
encmsg=pubkey.encrypt(msg);
alert(encmsg);
msg2=pvtkey.encrypt(encmsg);
alert(msg2);