1LUTSensor: Detecting FPGA Voltage Fluctuations using LookUp Tables

Remote Power Analysis (RPA) attacks use transient voltage fluctuation side channels detected via delay sensors/ on-chip voltage sensors to reveal secret keys from cryptographic circuits. The state-of-the-art research proposed five on-chip voltage sensors for Field Programmable Gate Arrays (FPGAs). This paper proposes a novel on-chip voltage sensor, 1LUTSensor, which uses FPGA LookUp Table (LUT) structure to deduce voltage fluctuations. 1LUTSensor uses LUT multiplexers to create a run-time adjustable delay line to detect voltage fluctuations and uses dedicated paths which are fabricated signal connections and cannot be changed in the FPGA LUT to form the delay line. 1LUTSensor uses only a single LUT and a single flip-flop for the delay line to sense voltage fluctuations and uses a single tapped delay element for calibration. The output of the 1LUTSensor is a single bit. Compared to the state-of-the-art on-chip sensors, 1LUTSensor proposed in this paper is the smallest and fastest on-chip voltage sensor proposed thus far. 1LUTSensor is at least 3x smaller than the smallest on-chip sensor proposed in the literature. Compared to the state-of-the-art, the proposed 1LUTSensor can be operated at 600MHz. 1LUTSensor is evaluated using RPA attacks, and a complete secret key of an AES circuit can be extracted within 100,000 traces.