An Asynchronous FPGA THx2 Programmable Cell for Mitigating Side-Channel Attacks

One approach to mitigate side-channel attacks (SCAs) is to use clockless, asynchronous digital logic. To simplify this process, we propose a unique asynchronous FPGA based on a new THx2 programmable threshold cell. At a minimum, FPGAs require a programmable logic cell that can implement a complete set of logic so that it can be connected through the programmable interconnect network to form any digital system. To meet that criteria, we take advantage of CMOS transistors to implement a programmable THx2 threshold cell capable of performing both TH12 and TH22 asynchronous operations. Our complete sixteen transistor FPGA cell includes eight transistors to implement the base THx2 threshold operation, three transistors to switch between the TH12 and TH22 modes, and five memory cell transistors for mode storage. Our unique minimal transistor, programmable THx2 implementation enables formation of a complete set of asynchronous threshold gates and a complete set of standard combinational logic functions. The symmetric nature of the FPGA cell, in regard to the number of transistors (eight NMOS and eight PMOS), makes it ideal for a four row by four column transistor grid with a nearly square, easily array-able layout. It should be noted our THx2 cell is highly compact and suitable for implementing a clockless, asynchronous FPGA.