Here, instead of encrypting a password, make the password a super-hard math problem.
Like this
<html>
<head>
<script language='javascript'>
var foo = 5 + 5 * 5;
var moo = foo * 2 * 4;
var goo = moo + foo % 7;
var too = goo * foo + moo;
var hoo = 6 / 2 + too * foo - moo + goo;
var poo = hoo / 50 * 0.04 - 80 % 9.9;
var doo = poo / 5 * 0.3 + 2 / 8;
var koo = doo * poo + hoo - foo % 7 / 8 * 3 / 500 % 29 / 5000 / 5 / 3 - 200000;
var yoo = doo + koo * 500000 / 6.1543 % 8.2543 / 4.4151 + 3135;
var voo = yoo * koo * 44252.45245 * poo * hoo * too * goo * moo * foo / 13.1345 % 170.908;
var joo = voo * 154213451.5245245 % 151.114354 / 4154.5454 + 27527272572.75272;
var noo = joo * 252542.245245 * 25254245.4524245 % 15.5135 / 2542.4524525;
var pass = noo * 52424532543245245 * 5245252425435 * 453435435 / 13 * 2152175621375.1534348343483;
</script>
</head>
<body>
<script language='javascript'>
function check(x)
{
if(x==pass){
alert('Correct Password');
window.location='';
}else{
alert('Incorrect Password');
}
}
</script>
<center><p>Please enter the password:</p><br /><input type="password" id="pass" value="" size='50' /><br />
<input type='button' onclick="check(document.getElementById('pass').value)" value='Check Password'>
</body>
</html>
Oh, and by the way, the password is:
7.114267799844692e+46