PUFKY: A Fully Functional PUF-Based Cryptographic Key Generator

Abstract

Abstract. We present PUFKY: a practical and modular design for a cryptographic key generator based on a Physically Unclonable Function (PUF). A fully functional reference implementation is developed and successfully evaluated on a substantial set of FPGA devices. It uses a highly optimized ring oscillator PUF (ROPUF) design, producing responses with up to 99% entropy. A very high key reliability is guaranteed by a syndrome construction secure sketch using an efficient and extremely low-overhead BCH decoder. This first complete implementation of a PUF-based key generator, including a PUF, a BCH decoder and a cryptographic entropy accumulator, utilizes merely 17% (1162 slices) of the available resources on a low-end FPGA, of which 82% are occupied by the ROPUF and only 18% by the key generation logic. PUFKY is able to produce a cryptographically secure 128-bit key with a failure rate < 10 −9 in 5.62 ms. The design's modularity allows for rapid and scalable adaptations for other PUF implementations or for alternative key requirements. The presented PUFKY core is immediately deployable in an embedded system, e.g. by connecting it to an embedded microcontroller through a convenient bus interface.

Large scale RO PUF analysis over slice type, evaluation time and temperature on 28nm Xilinx FPGAs

“…A number of different algorithms have been proposed in the literature, such as the original RO-PUF proposal [6], the PUFKY [1] or the SUM-PUF [18]. In order to not limit our analysis to a specific algorithm we only implemented the core RO on the FPGA.…”

“…where σ is the standard deviation among repetitions and N the number of repetitions, which equals D/D et in our case 1 . Thus, the standard deviation of the sample mean can be written as a function of the overall evaluation time D…”

“…Two applications can be built upon the information provided by a PUF output, or response, which is unique to the physical device: Extraction of secret keys, e.g. for encryption [1], [2], and challenge-response based authentication protocols [3], [4].…”

Efficient Fuzzy Extraction of PUF-Induced Secrets: Theory and Applications

“…Currently, secure sketch implementations rely on the (n − k) upper bound on the min-entropy loss, e.g., [23]. Unfortunately, this leads to an overly conservative design when instantiating security parameters accordingly.…”

“…Prior work focussed on repetition codes only. Although frequently used as the inner code of a concatenated code [5], full-fledged key generators [23] typically rely on non-trivial codes, e.g., BCH codes [18]. Second, our techniques may be applied to a variety of distributions, while prior work covered biased distributions only.…”