Communication Dans Un Congrès Année : 2025

SIFA on Nonce-based Authenticated Encryption: When Does It Fail? Application to Ascon

Résumé

In nonce-based authenticated encryption schemes, fault attacks such as differential fault analysis are not applicable to due to the uniqueness of the nonce. In this context, Dobraunig et al. (SAC 2018) showed that Statistical Ineffective Fault Attacks (SIFA) remain applicable and powerful. The authors proposed a SIFA-based attack strategy targeting the initialization in nonce-based authenticated encryption schemes and demonstrated its practicality using a common fault method: instruction skip. In this work, we provide a more in-depth analysis of this attack strategy, with a focus on instruction skip as the fault method. First, we model common instruction skip scenarios in practice and formalize the probability that a fault is ineffective. Our analysis reveals that this probability depends on the instruction type and the device architecture. Notably, we show that it is practically inefficient to obtain a sufficient number of ineffective faults for SIFA when skipping an XOR instruction on 32-bit or 64-bit systems, where register data tends to be uniformly distributed. Second, we prove that, in certain authenticated encryption implementations, the intermediate value targeted by the attack unexpectedly remains unbiased under ineffective faults, making SIFA inapplicable. As a case study, we demonstrate this behavior in an 8-bit Ascon implementation.

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Dates et versions

hal-05253276 , version 1 (14-09-2025)

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  • HAL Id : hal-05253276 , version 1

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Viet Sang Nguyen, Vincent Grosso, Pierre-Louis Cayrel. SIFA on Nonce-based Authenticated Encryption: When Does It Fail? Application to Ascon. Workshop on Fault Detection and Tolerance in Cryptography (FDTC 2025), Sep 2025, Kuala Lumpur, Malaysia. ⟨hal-05253276⟩
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