The threats of physical side-channel attacks and their countermeasures have been widely researched. Most physical side-channel attacks rely on the unavoidable influence of computation or storage on current consumption or voltage drop on a chip. Such data-dependent influence can be exploited by, for instance, power or electromagnetic analysis. In this work, we introduce a novel non-invasive physical side-channel attack, which exploits the data-dependent changes in the impedance of the chip. Our attack relies on the fact that the temporarily stored contents in registers alter the physical characteristics of the circuit, which results in changes in the die's impedance. To sense such impedance variations, we deploy a well-known RF/microwave method called scattering parameter analysis, in which we inject sine wave signals with high frequencies into the system's power distribution network (PDN) and measure the echo of the signals. We demonstrate that according to the content bits and physical location of a register, the reflected signal is modulated differently at various frequency points enabling the simultaneous and independent probing of individual registers. Such side-channel leakage challenges the t-probing security model assumption used in masking, which is a prominent side-channel countermeasure. To validate our claims, we mount non-profiled and profiled impedance analysis attacks on hardware implementations of unprotected and high-order masked AES. We show that in the case of the profiled attack, only a single trace is required to recover the secret key. Finally, we discuss how a specific class of hiding countermeasures might be effective against impedance leakage.
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Circuit Masking Schemes: New Hope for Backside Probing Countermeasures?
Sensitive data can be extracted by mounting physical attacks, e.g., photon emission analysis, micro-probing, etc., on integrated circuits (ICs). In this paper, our ultimate goal is to examine provable security approaches that increase the number of simultaneous probes needed to perform probing in order to see how they can complement physical anti-probing countermeasures. Commonly applied mathematical models for probing attacks have employed randomized bits to mask the input, and modified computations. As the number of masks increases, the number of probes needed to extract the secret data increases linearly, assuming noise-free conditions. In another attempt, noisy leakage models have been developed to better mimic real-world scenarios, but their complexity is a major drawback. Hence, extensive research has been performed to show connections between noisy leakage models and probing models. The goal of this survey is to relate the notion of masking with
physical backside attack countermeasures, which are limited in practice. To this end, our first milestone is to unify provable probing and side-channel models in order to develop and realize more practical countermeasures.
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- Award ID(s):
- 1717392
- PAR ID:
- 10173592
- Date Published:
- Journal Name:
- SRC TECHCON
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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