Cryptology ePrint Archive: Report 2018/852

Fault Attacks on Nonce-based Authenticated Encryption: Application to Keyak and Ketje

Christoph Dobraunig and Stefan Mangard and Florian Mendel and Robert Primas

Abstract: In the context of fault attacks on nonce-based authenticated encryption, an attacker faces two restrictions. The first is the uniqueness of the nonce for each new encryption that prevents the attacker from collecting pairs of correct and faulty outputs to perform, e.g., differential fault attacks. The second restriction concerns the verification/decryption, which releases only verified plaintext. While many recent works either exploit misuse scenarios (e.g. nonce-reuse, release of unverified plaintext), we turn the fact that the decryption/verification gives us information on the effect of a fault (whether a fault changed a value or not) against it. In particular, we extend the idea of statistical ineffective fault attacks (SIFA) to target the initialization performed in nonce-based authenticated encryption schemes. By targeting the initialization performed during decryption/verification, most nonce-based authenticated encryption schemes provide the attacker with an oracle whether a fault was ineffective or not. This information is all the attacker needs to mount statistical ineffective fault attacks. To demonstrate the practical threat of the attack, we target software implementations of the authenticated encryption schemes Keyak and Ketje. The presented fault attacks can be carried out without the need of sophisticated equipment. In our practical evaluation the inputs corresponding to 24 ineffective fault inductions were required to reveal large parts of the secret key in both scenarios.

Category / Keywords: secret-key cryptography / Fault Attack, Statistical Ineffective Fault Attack, SIFA, Authenticated Encryption, Keyak, Ketje

Original Publication (with minor differences): Selected Areas in Cryptography (SAC) 2018

Date: received 8 Sep 2018, last revised 21 Sep 2018

Contact author: robert primas at iaik tugraz at

Available format(s): PDF | BibTeX Citation

Note: Just added acknowledgements

Version: 20180921:070241 (All versions of this report)

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