Psst, Over Here: Communicating Without Fixed Infrastructure

This paper discusses a way to communicate without relying on fixed infrastructure at some central hub. This can be useful for bootstrapping loosely connected peer-topeer systems, as well as for circumventing egregious policy-based blocking (e.g., for censorship purposes). Our techniques leverage the caching and aging properties of DNS records to create a covert channel of sorts that can be used to store ephemeral information. The only requirement imposed on the actors wishing to publish and/or retrieve this information is that they share a secret that only manifests outside the system and is never directly encoded within the network itself. We conduct several experiments that illustrate the efficacy of our techniques to exchange an IP address that is presumed to be a rendezvous point for future communication. Additionally, we describe a wider channel that can be used to transmit an SMSor Twitter-like 140-character message.