A 2 Bit/Cell Tilting SRAM-Based PUF With a BER of 3.1E-10 and an Energy of 21 FJ/Bit in 65nm

An SRAM-based Physical Unclonable Function (PUF) with two independent bits/cells is presented along with a tilting preselection test designed to identify all the unstable bits. Results of analysis of the Decision Voltage of the SRAM-based PUF cell indicate that in certain conditions, only the NMOS transistors in the cell impact its response, whereas the PMOS devices are in cutoff. Two pairs of NMOS transistors are inserted in the cell, each of which represents an orthogonal bit. The tilt test evaluates the internal mismatch within each of the NMOS pairs so that if it is insufficient, the resulting bit is considered unstable and masked from the PUF response. The cell demonstrated a highly competitive area of 1420F
²
per bit, a bit-error-rate (BER) of 3.1E-10, and a very low energy consumption of 21fJ/bit in 65nm. After preselection, the 2 bit/cell PUF exhibited a near-ideal inter-chip Hamming distance (49.5%) and percentage of ones (50.6%).