Insider Attacks Enabling Data Broadcasting on Crypto-Enforced Unicast Links

Most wireless communication techniques rely on broadcast media on the physical layer, i.e., the actual signal can be received by any party in a certain coverage area. Furthermore, there are cable-based networks, such as HFC (hybrid fiber/coaxial) networks that use a shared transmission medium (coaxial cable) to bridge the last mile. A common means to perform secure unicast (point-to-point) communication over such wireless or shared transmission media is by applying cryptographic protocols on higher layers of the protocol stack. As of today, a common assumption in the design and analysis of such communication protocols is that both end-points (user and carrier) behave correctly according to the cryptographic protocol, because they want to preserve security against outsiders who might be sniffing private communication of legitimate users. However, under certain conditions users may not be interested in protecting their unicast communication against outsiders. Instead, users may try to extend their communication power/resources by means of insider attacks against the communication protocol. Such insider attacks pose new threats to providers of communication services and have, to the best of our knowledge, been neglected so far. In this paper we will discuss insider attacks against several communication systems that can break the unicast communication enforced by cryptographic means by the carrier of the communication infrastructure.