## Cryptology ePrint Archive: Report 2017/984

Self-Guarding Cryptographic Protocols against Algorithm Substitution Attacks

Marc Fischlin and Sogol Mazaheri

Abstract: We put forward the notion of self-guarding cryptographic protocols as a countermeasure to algorithm substitution attacks. Such self-guarding protocols can prevent undesirable leakage by subverted algorithms if one has the guarantee that the system has been properly working in an initialization phase. Unlike detection-based solutions they thus proactively thwart attacks, and unlike reverse firewalls they do not assume an online external party.

We present constructions of basic primitives for (public-key and private-key) encryption and for signatures. We also argue that the model captures attacks with malicious hardware tokens and show how to self-guard a PUF-based key exchange protocol.

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