This paper presents PFC (Private Facebook Chat), a system that provides end-to-end encryption for Facebook Chat sessions so that eavesdroppers (including Facebook itself) cannot access chat messages. The system is designed with goodenough security to thwart eavesdroppers. Security overlays provide a distinct interface on top of the existing Facebook
interface so that the plaintext of a chat conversation is not available to Facebook or anyone who could modify a Facebook
page during transmission. The primary design focus is on making the system easy to use.