Impact of Operating Conditions on the Reliability of SRAM-Based Physical Unclonable Functions (PUFs)

Wireless sensor systems can collect and share a large amount of data for different kinds of applications, but are also vulnerable to cyberattacks. The impact of cyberattacks on systems’ confidentiality, integrity, and availability can be mitigated by using authentication procedures and cryptographic algorithms. Authentication passwords and cryptographic keys may be stored in a non-volatile memory, which may be easily tampered with. Alternately, Physical Unclonable Functions (PUFs) can be adopted. They generate a chip’s unique fingerprint, by exploiting the randomness of process parameters’ variations occurring during chip fabrication, thus constituting a more secure alternative to the adoption of non-volatile memories for password storage. PUF reliability is of primary concern to guarantee a system’s availability. In this paper, the reliability of a Static Random Access Memory (SRAM)-based PUF implemented by a standard 32 nm CMOS technology is investigated, as a function of different operating conditions, such as noise, power supply voltage, and temperature, and considering different values of transistor conduction threshold voltages. The achieved results will show that transistor threshold voltage and noise are the operating conditions mostly affecting PUF reliability, while the impact of temperature variations is lower, and that of power supply variations is negligible.