Efficient Erasable PUFs from Programmable Logic and Memristors

At Oakland 2013, Rührmair and van Dijk showed that many advanced PUF (Physical Unclonable Function)-based security protocols (e.g. key agreement, oblivious transfer, and bit commitment) can be vulnerable if adversaries get access to the PUF and reuse the responses used in the protocol after the protocol execution. This observation implies the necessity of erasable PUFs for realizing secure PUF-based protocols in practice. Erasable PUFs are PUFs where the responses of any single challengeresponse pair (CRP) can be selectively and dedicatedly erased, without affecting any other responses. In this paper, we introduce two practical implementations of erasable PUFs: Firstly, we propose a full-fledged logical version of an erasable PUF, called programmable logically erasable PUF or PLayPUF, where an additional constant-size trusted computing base keeps track of the usage of every single CRP. Knowing the query history of each CRP, a PLayPUF interface can automatically erase an individual CRP, if it has been used for a certain number of times. This threshold can be programmed a-priori to limit the usage of a given challenge in the future before erasure. Secondly, we introduce two nanotechnological, memristor-based solutions: mrSHICPUFs and erasable mrSPUFs. The mrSHIC-PUF is a weak PUF in terms of the size of CRP space, and therefore its readout speed has to be limited intentionally to prolong the time for exhaustive reading. However, each individual response can be physically altered and erased for good. The erasable mrSPUF, as the second proposed physical erasable PUF, is a strong PUF in terms of the size of CRP space, such that no limit on readout speed is needed, but it can only erase/alter CRPs in groups. Both of these two physical erasable PUFs improve over the state-of-the-art erasable SHIC PUF, which does not offer reconfigurability of erased CRPs making the erasable SHIC PUF less practical. ∗Yansong Gao and Chenglu Jin are in alphabetical order and share first authorship. Yansong Gao contributed to Section 4 under the supervision of Damith C. Ranasinghe. Chenglu Jin contributed to Section 2 and 3 under the supervision of Marten van Dijk. Jeeson Kim, Hussein Nili and Omid Kavehei were in charge of fabricating the memristor based erasable PUFs. Xiaolin Xu and Wayne Burleson helped with implementing the PUF circuitry for the programmable logically erasable PUF. Ulrich Rührmair conceived and led the whole project. 2 Efficient Erasable PUFs from Programmable Logic and Memristors Figure 1: PUF based session key exchange involved three parties. In passing, we contextualize and locate our new PUF type in the existing landscape, illustrating their essential advantages over variants like reconfigurable PUFs.