Testing 90 nm microcontroller SRAM PUF quality

In digital systems, Static Random Access Memories (SRAMs) play an important role since they are available in almost every digital devices and are able to realize Physically Unclonable Functions (PUFs), which can enable security primitives over a wide range of devices without needing additional hardware resources. Indeed, each SRAM presents an unpredictable and unique pattern, established when they are powered-up, which can be useful as key generator and for authentication mechanisms. Before exploiting SRAMs as PUFs, they have to be qualified in terms of stability since the pattern behavior of SRAMs might be heavily influenced by a wide variety of working conditions, such as temperature and applied voltage. In this paper we present the result of an experimental campaign, conducted over real 90nm SRAMs, which aim is to deeply investigate the power-up pattern behavior under different power supply strategies through the PUF quality analysis. In particular we show the reliability, uniqueness and uniformity for SRAMs embedded in STM32F3 and STM32F4 microcontrollers for more than 50 devices.