Abstract
Static Random Access Memory (SRAM) Physical Unclonable Functions (PUFs) are some of the most popular PUFs that provide a highly-secured solution for secret key storage. Given that PUF responses are noisy, the key reconstruction must use error correcting code (ECC) to reduce the noise. Repetition code is widely used in resource constrained systems as it is concise and lightweight, however, research has shown that repetition codes can lead to information leakage. In this paper we found that the strongest cell distribution in a SRAM array may leak information of the responses of SRAM PUF when the repetition code is directly applied. Experimentally, on an ASIC platform with the HHGRACE 0.13 μm process, we recovered 8.3% of the measured response using the strongest cells revealed by the helper data, and we finally obtained a clone response 79% similar to weak response using the public helper data. We therefore propose Error Resistant Fuzzy Extractor (ERFE), a 4-bit error tolerant fuzzy extractor, that extracts the value of the sum of the responses as a unique key and reduces the failure rate to 1.8 × 10−8 with 256 bit entropy.
Highlights
Electronic devices have never been used so widely in our lives as
Among these Physical Unclonable Functions (PUFs), Static Random Access Memory (SRAM) PUF is widely used because of the following advantages [11,12]: (1) SRAM is a standard component existing on different process nodes, and (2) many chips have built-in SRAM arrays as caches and temporary data storage units that can be used as PUFs to generate Challenge-Response pairs (CRPs) without requiring additional design and area overhead compared to other types of PUFs
We analyzed the physical challenge space of SRAM PUFs, and found a weak response in the SRAM PUF based on a repetition code
Summary
Electronic devices have never been used so widely in our lives as now. With the dramatic development of electronic payments, tag applications, and Internet of Things (IoTs), the issue of equipment security issue has become increasingly severe, in the generation, distribution, storage, and destruction of secret keys [1,2]. PUFs have weak responses when a repetition code is directly used, and the distribution of the strongest cells in the SRAM array further reduces the leftover entropy of the PUF. We first propose a method to recover the response using the helper data from a SRAM PUF with the distribution of the strongest cells. The structure of this paper is as follows: in Section 2, we review the structure and characteristics of SRAM PUFs. In Section 3, we study and analyze the weakness of SRAM PUFs based on repetition code and use the helper data generated by the weak responses to generate a clone of the power-on value of the SRAM.
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