Recent research has shown that the integrity of sensor measurements can be violated through out-of-band signal injection attacks. These attacks target the conversion process from a physical quantity to an analog property-a process that fundamentally cannot be authenticated. Out-of-band signal injection attacks thus pose previously-unexplored security risks by exploiting hardware imperfections in the sensors themselves, or in their interfaces to microcontrollers. In response to the growingyet-disjointed literature in the subject, this article presents the first survey of out-of-band signal injection attacks. It focuses on unifying their terminology and identifying commonalities in their causes and effects through a chronological, evolutionary, and thematic taxonomy of attacks. By highlighting cross-influences between different types of out-of-band signal injections, this paper underscores the need for a common language irrespective of the attack method. By placing attack and defense mechanisms in the wider context of their dual counterparts of side-channel leakage and electromagnetic interference, this study identifies common threads and gaps that can help guide and inform future research. Overall, the ever-increasing reliance on sensors embedded in everyday commodity devices necessitates that a stronger focus be placed on improving the security of such systems against out-of-band signal injection attacks.

Recent investigations into FPGA routing resources have shown that long wires in FPGAs leak information about their state in a way which can be measured using ring oscillators. Although in many cases this leakage does not pose a security threat, the possibility of multi-tenant use of FPGA resources invites potential side-and covert-channel attacks exploiting long wire leakage. However, prior work has ignored the realities of cloud environments, which may pose restrictions on the generated bitstreams, such as disallowing combinatorial loops. In this paper, we first demonstrate that the long wire leakage phenomenon persists even in the high-end Virtex UltraScale+ FPGA family. We then evaluate two ring oscillator designs that overcome combinatorial loop restrictions employed by cloud FPGA providers. We experimentally measure the long wire leakage of Virtex UltraScale+ FPGAs in the lab as well as in the Amazon and Huawei FPGA clouds. We show that the two new ring oscillator designs provide almost-identical estimates for the strength of the leakage as traditional ring oscillators, allowing us to measure femtosecond-scale changes in the delays of the long wires. We finally present a set of defense mechanisms that can prevent the new ring oscillator designs from being instantiated in the cloud and the long wire leakage from being exploited.

No abstract

No abstract