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.
- Cryogenic cooling disables clock and voltage sensors without electrical tampering
- Chypothermia plus Chypnosis halts clocks while evading temperature-anomaly detection
- Demonstrated against OpenTitan alert handler, preventing key zeroization
- Proposes FPGA-compatible self-heating sensor as countermeasure
Full article233 words · extracted from arxiv.org · click to collapse
Static side-channel attacks, which exploit halted-clock conditions to extract sensitive information, pose an increasing threat to chip security. To counter these attacks, various defenses have been proposed that monitor for abnormal clock behavior and trigger the clearing of sensitive data when clock anomalies are detected. In this work, we demonstrate that exposing a chip to cryogenic temperatures interferes with on-chip mixed-signal components, responsible for signal sensing and generation. Based on this observation, we develop Chypothermia, an attack that, without any electrical tampering with the system, disables the target clock sensor, the clock generation circuit, and the voltage sensors, while preserving the secret data. While effective at halting the clock, cooling is a slow process and, on its own, is often insufficient against systems equipped with temperature sensors designed to detect thermal anomalies. To bypass these protections, we combine Chypothermia with Chypnosis (Mitard et al., IEEE SP 2026) and show that, even within a moderately low-temperature operating range, this combination can halt the clock while evading detection. We implement Chypothermia on multiple FPGA/SoC platforms and demonstrate successful disabling of both soft-IP and hard-IP sensor implementations. Finally, we apply Chypothermia to the alert handler of the OpenTitan root of trust, which incorporates a state-of-the-art clock sensor, and show that the attack evades detection and prevents key zeroization. Finally, we introduce and implement an FPGA-compatible self-heating sensor as a countermeasure and demonstrate its robustness against Chypothermia.
Text extracted automatically; images, tables and formatting may be missing. Original: https://arxiv.org/abs/2609.11442