Practical Non-Invasive Probing Attacks Against Novel Carbon-Nanotube-Based Physical Unclonable Functions

As the number of devices being interconnected increases, so does also the demand for (lightweight) security. To this end, Physical Unclonable Functions (PUFs) have been proposed as hardware primitives that can act as roots of trust and security. Recently, a new type of PUF based on Carbon NanoTubes (CNTs) has been proposed. At the same time, attacks and testing based on direct electrical probing appear to be moving towards non-invasive techniques. In this context, this work attempts to examine the potential for practical non-invasive probing attacks against the CNT-PUF, a novel PUF based on CNTs. Our results indicate that direct probing might potentially compromise the security of this PUF. Nevertheless, we note that this holds true only in the case that the attacker can directly probe the wire corresponding to the secret value of each CNT-PUF cell. Thus, we can conclude that the examined CNT-PUFs are rather resilient to direct probing attacks, that non-invasive probing methods appear to be promising for testing such PUFs, and that, in order for the attacker to gain the full-length value of the secret, all the relevant channels would need to be probed. Nevertheless, as our work proves, practical non-invasive attacks against the CNT-PUF are feasible and adequate countermeasures need to be employed in order to address this issue.