Physical Characterization of Arbiter PUFs

As intended by its name, Physically Unclonable Functions PUFs are considered as an ultimate solution to deal with insecure storage, hardware counterfeiting, and many other security problems. However, many different successful attacks have already revealed vulnerabilities of certain digital intrinsic PUFs. Although settling-state-based PUFs, such as SRAM PUFs, can be physically cloned by semi-invasive and fully-invasive attacks, successful attacks on timing-based PUFs were so far limited to modeling attacks. Such modeling requires a large subset of challenge-response-pairs CRP to successfully model the targeted PUF. In order to provide a final security answer, this paper proves that all arbiter-based i.e. controlled and XOR-enhanced PUFs can be completely and linearly characterized by means of photonic emission analysis. Our experimental setup is capable of measuring every PUF-internal delay with a resolution of 6 picoseconds. Due to this resolution we indeed require only the theoretical minimum number of linear independent equations i.e. physical measurements to directly solve the underlying inhomogeneous linear system. Moreover, we neither require to know the actual PUF challenges nor the corresponding PUF responses for our physical delay extraction. On top of that devastating result, we are also able to further simplify our setup for easier physical measurement handling. We present our practical results for a real arbiter PUF implementation on a Complex Programmable Logic Device CPLD from Altera manufactured in a 180 nanometer process.