TIGER: TrIaGing KEy Refreshing Frequency via Digital Sensors

Abstract

Key refreshing is a pragmatic countermeasure to side-channel attacks, designed to revoke and replace the key promptly when an attack is either anticipated or suspected. This system-level approach rekeys the device under attack and keeps paired devices protected if cryptography secures data in transit. The frequency of key refreshing is critical: too infrequent, and security risks increase; too frequent, and system performance degrades. This frequency is set pre-silicon via threat analysis but may be inefficient as leakage varies with operating conditions. To fill the gap, we introduce a post-silicon strategy for optimal rekeying frequency. Our proposed scheme TIGER deploys a digital sensor to monitor environmental conditions and enabling inference at runtime by pre-characterizing the leakage rate correlated to the digital sensor measurements. The accumulated leakage rate helps deduce a cutoff time for rekeying. We demonstrate the end-to-end feasibility of this approach on an FPGA board designed for side-channel threat assessment.