Charge 2 - Stripe form fields not showing
After looking into the source code of the encrypt function, the craft.charge.setPaymentOptions() function calls mcrypt_module_get_algo_key_size and because my vagrant box (ubuntu 14.04) didn't have php5-mcrypt installed, it failed there.

To fix it: run apt-get install php5-mcrypt &amp;&amp; sudo php5enmod mcrypt.