Sensing nanosecond-scale voltage attacks and natural transients in FPGAs

Voltage noise not only detracts from reliability and performance, but has been used to attack system security. Most systems are completely unaware of fluctuations occurring on nanosecond time scales. This paper quantifies the threat to FPGA-based systems and presents a solution approach. Novel measurements of transients on 28nm FPGAs show that extreme activity in the fabric can cause enormous undershoot and overshoot, more than 10× larger than what is allowed by the specification. An existing voltage sensor is evaluated and shown to be insufficient. Lastly, a sensor design using reconfigurable logic is presented; its time-to-digital converter enables sample rates 500× faster than the 28nm Xilinx ADC. This enables quick characterization of transients that would normally go undetected, thereby providing potentially useful data for system optimization and helping to defend against supply voltage attacks.