Cryptology ePrint Archive: Report 2013/679

Formal verification of a software countermeasure against instruction skip attacks

Nicolas Moro and Karine Heydemann and Emmanuelle Encrenaz and Bruno Robisson

Abstract: Fault attacks against embedded circuits enabled to define many new attack paths against secure circuits. Every attack path relies on a specific fault model which defines the type of faults that the attacker can perform. On embedded processors, a fault model consisting in an assembly instruction skip can be very useful for an attacker and has been obtained by using several fault injection means. To avoid this threat, some countermeasure schemes which rely on temporal redundancy have been proposed. Nevertheless, double fault injection in a long enough time interval is practical and can bypass those countermeasure schemes. Some fine-grained countermeasure schemes have also been proposed for specific instructions. However, to the best of our knowledge, no approach that enables to secure a generic assembly program in order to make it fault-tolerant to instruction skip attacks has been formally proven yet. In this paper, we provide a fault-tolerant replacement sequence for almost all the instructions of the Thumb-2 instruction set and provide a formal verification for this fault tolerance. This simple transformation enables to add a reasonably good security level to an embedded program and makes practical fault injection attacks much harder to achieve.

Category / Keywords: microcontroller, fault attack, instruction skip, countermeasure, formal verification

Original Publication (with minor differences): Journal of Cryptographic Engineering

Date: received 23 Oct 2013, last revised 24 Feb 2014

Contact author: nicolas moro at mines-stetienne fr

Available format(s): PDF | BibTeX Citation

Note: Extended version of the article presented in the PROOFS 2013 workshop.

The final article has been published in the Journal of Cryptographic Engineering (DOI 10.1007/s13389-014-0077-7), this preliminary version has been submitted to the IACR ePrint archive for self-archiving.

Version: 20140224:143404 (All versions of this report)

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