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Formalism to assess the entropy and reliability of the loop-PUF

Jean-Luc Danger 1, 2 Olivier Rioul 3, 2 Sylvain Guilley 1, 2 Alexander Schaub 3, 2
1 SSH - Secure and Safe Hardware
LTCI - Laboratoire Traitement et Communication de l'Information
3 COMNUM - Communications Numériques
LTCI - Laboratoire Traitement et Communication de l'Information
Abstract : Many Methods exist for Physically Unclonable Function in order to enhance their reliability, but they are at the cost of extra hard- ware, either coming from the PUF core itself, or from the correction method, as fuzzy extraction [5]. Another issue is to better know the PUF entropy, especially when the PUF is used as a cryptographic key generator. The SRAM and Ring Oscillator PUF provide relatively high entropy, as shown experimentally in [4]. The min-entropy is gen- erally better assessed, as studied in Delvaux et al. [2] which presents the min-entropy of strong PUFs. For strong PUFs, it appears that the number of required challenges to get the min-entropy is signif- ficantly higher, thus involving compression and extra complexity to generate key bits. We show in this study that it is possible to ob- tain a strong PUF, relying on a Loop PUF, which presents a high ratio between reliability and complexity. Moreover the entropy can be known when choosing the minimal and optimal number of chal- lenges, namely Hadamard Codes. As the presence of noise inevitably involves an entropy decrease, this paper presents a method allowing the PUF to compensate this loss to meet the requires entropy. The single Ring-Oscillator of the Loop PUF, the hard-coded challenges and the lightweight error correction provide a low complexity PUF, around 1000 μm2 , with an access time of 20 ms to get a 64 key bits with a Bit Error Rate (BER) which can be less than 10−9 by filter- ing unreliable bits. As the challenges and responses remain local, the modeling attacks are signiffificantly reduced and are not considered in this work.
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Submitted on : Friday, September 13, 2019 - 5:08:02 PM
Last modification on : Friday, July 31, 2020 - 11:28:08 AM


  • HAL Id : hal-02287598, version 1


Jean-Luc Danger, Olivier Rioul, Sylvain Guilley, Alexander Schaub. Formalism to assess the entropy and reliability of the loop-PUF. 15th International Workshop on Cryptographic Architectures Embedded in Reconfigurable Devices (CryptArchi 2017), Jun 2017, Smolenice, Slovakia. ⟨hal-02287598⟩



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