Single-Chip Motes and SRAM PUF: Feasibility Study

Physically unclonable functions (PUFs) are used as low-cost cryptographic primitives that extract keying material from manufacturing variabilities of a device. All microcontrollers have on-chip SRAM; the power-up state of SRAM cells provides one way of obtaining a random output. However, not every SRAM can be used as a PUF. SRAM PUFs need to fulfill certain requirements: randomness, reliability, unpredictability and uniqueness. In this paper, we study whether the SRAM present on a novel class of devices, single-chip motes, satisfies these requirements. Single-chip motes are wireless sensor nodes that integrate computation, communication, power and sensing on a single chip. We analyze the SRAM characteristics on nine different single-chip motes to understand the potential of using these integrated SRAMs as PUF. Our experiments on 55 kB SRAM for each mote indicate that SRAM start-up values satisfy the requirements. Therefore, these embedded memories can be used for different PUF applications, including secret key extraction and true random number generation.