Distributed systems have become a standard method of operation for Internet-based services. While there exist methods to prove the authenticity and secure operation of a single remote party, it is not currently possible to efficiently obtain these same guarantees of a distributed system. Thus, in this work we present PortAuthority: a service which carefully manages connections and only authorizes input data from provably secure remote parties. To examine its effectiveness, we compare the performance of several different systems with and without the PortAuthority service. We show that PortAuthority is able to provide these guarantees without a significant overhead and independent of the communicating applications, with the only noticeable delay occurring at the initial connection setup.