Paper 2020/145

Self-Secured PUF: Protecting the Loop PUF by Masking

Lars Tebelmann, Jean-Luc Danger, and Michael Pehl


Physical Unclonable Functions (PUFs) provide means to generate chip individual keys, especially for low-cost applications such as the Internet of Things (IoT). They are intrinsically robust against reverse engineering, and more cost-effective than non-volatile memory (NVM). For several PUF primitives, countermeasures have been proposed to mitigate side-channel weaknesses. However, most mitigation techniques require substantial design effort and/or complexity overhead, which cannot be tolerated in low-cost IoT scenarios. In this paper, we first analyze side-channel vulnerabilities of the Loop PUF, an area efficient PUF implementation with a configurable delay path based on a single ring oscillator (RO). We provide side-channel analysis (SCA) results from power and electromagnetic measurements. We confirm that oscillation frequencies are easily observable and distinguishable, breaking the security of unprotected Loop PUF implementations. Second, we present a low-cost countermeasure based on temporal masking to thwart SCA that requires only one bit of randomness per PUF response bit. The randomness is extracted from the PUF itself creating a self-secured PUF. The concept is highly effective regarding security, low complexity, and low design constraints making it ideal for applications like IoT. Finally, we discuss trade-offs of side-channel resistance, reliability, and latency as well as the transfer of the countermeasure to other RO-based PUFs.

Note: The paper was published at COSADE 2020.

Available format(s)
Publication info
Published elsewhere. COSADE 2020
Physically Unclonable FunctionSide-Channel AnalysisRO PUFLoop PUFMaskingCountermeasureIoT
Contact author(s)
lars tebelmann @ tum de
2021-02-10: revised
2020-02-10: received
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Creative Commons Attribution


      author = {Lars Tebelmann and Jean-Luc Danger and Michael Pehl},
      title = {Self-Secured PUF: Protecting the Loop PUF by Masking},
      howpublished = {Cryptology ePrint Archive, Paper 2020/145},
      year = {2020},
      doi = {10.1007/978-3-030-68773-1_14},
      note = {\url{}},
      url = {}
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