Chypothermia: Clock Freezing for Static Side-channel Attacks
Chypothermia attack uses cryogenic cooling to disable clock and voltage sensors, evading detection and blocking key zeroization on OpenTitan root of trust.
Chypothermia is a static side-channel attack that exposes chips to cryogenic temperatures, disrupting on-chip mixed-signal components to disable the clock sensor, clock generation circuit, and voltage sensors without electrical tampering. Combined with Chypnosis (IEEE S&P 2026), it halts the clock while evading temperature-based anomaly detection. It was implemented on multiple FPGA/SoC platforms and applied to the OpenTitan root of trust's alert handler, evading detection and preventing key zeroization. The authors also propose an FPGA-compatible self-heating sensor as a countermeasure.
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