Cryptology ePrint Archive: Report 2022/565

Power Contracts: Provably Complete Power Leakage Models for Processors

Roderick Bloem and Barbara Gigerl and Marc Gourjon and Vedad Hadžić and Stefan Mangard and Robert Primas

Abstract: The protection of cryptographic software implementations against power-analysis attacks is critical for applications in embedded systems. A commonly used algorithmic countermeasure against these attacks is masking, a secret-sharing scheme that splits a sensitive computation into computation on multiple random shares. In practice, the security of masking schemes relies on several assumptions that are often violated by microarchitectural side-effects of CPUs. Many past works address this problem by studying these leakage effects and building corresponding leakage models that can then be integrated into a software verification workflow. However, these models have only been derived empirically, putting the otherwise rigorous security statements made with verification in question.

We solve this problem in two steps. First, we introduce a contract layer between the (CPU) hardware and the software that allows the specification of microarchitectural side-effects on masked software in an intuitive language. Second, we present a method for proving the correspondence between contracts and CPU netlists to ensure the completeness of the specified leakage models. Then, any further security proofs only need to happen between software and contract, which brings benefits such as reduced verification runtime, improved user experience, and the possibility of working with vendor-supplied contracts of CPUs whose design is not available on netlist-level due to IP restrictions. We apply our approach to the popular RISC-V IBEX core, provide a corresponding formally verified contract, and describe how this contract could be used to verify masked software implementations.

Category / Keywords: foundations / Power Side-Channel, Leakage Model, Verification, Contract, Domain-Specific Language, Masking, Probing Security

Date: received 9 May 2022

Contact author: vedad hadzic at iaik tugraz at

Available format(s): PDF | BibTeX Citation

Version: 20220510:082439 (All versions of this report)

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