Assessment of an FPGA Implementation of a Hybrid PUF Based on a Configurable Transient Effect Ring Oscillator and Ring Oscillator (TERORO-PUF)

In the current situation of the Internet of Things (IoT) with its billions of interconnected devices, security in this low-resource environment is paramount. A Physical Unclonable Function (PUF) is a very useful cryptographic primitive which allows us to extract unique information from a particular device in a non-reproducible way. This allows us to use a PUF in cryptography for authentication or secret-key generation. Ring Oscillators (ROs) and Transient Effect Ring Oscillators (TEROs) are oscillating structures used in both FPGAs and ASICs to build PUFs. In this paper we present an FPGA implementation of a PUF based on what we call the “TERORO” cell (TERO + RO), which is a hybrid structure that allows us to use the different functionalities of both RO and TERO in a single building block. We assess all the possible methods of extracting bits of information from the PUF based on TERORO cells. Finally, we tested the circuit and presented experimental results in terms of its uniqueness, uniformity, and reliability. In RO-counter mode, we obtain 49.74% uniqueness, 54.66% uniformity, and 97.81% reliability across devices, while TERO-based XOR mixing achieves 52.83% uniformity, 45.79% uniqueness, and 93.15% reliability. The FPGA footprint is 142 LUTs, 36 registers, and 82 slices.