function hex_sha(string, variant)
{
	var shaObj = new jsSHA(string);
	return shaObj.getHash(variant, "HEX");
}

function secureLogin()
{
	var password = $('password').value;
	var challenge = $('challenge').value;
	
	var hashedPassword = hex_sha(hex_sha(password, 'SHA-512')+challenge, 'SHA-512');
	
	$('password').disabled = true;
	$('hashedPassword').value = hashedPassword;
	$('password').value = '';
	for(i = 0; i < password.length; i++)
		$('password').value += '*';
}