Abstract
Evaluating the practical security of Ring-LWE based cryptography has attracted lots of efforts recently. Indeed, some differences from the standard LWE problem enable new attacks. In this paper we discuss the security of Ring-LWE as found in Fully Homomorphic Encryption (FHE) schemes. These FHE schemes require parameters of very special shapes, that an attacker might use to its advantage. First we present the specificities of this case and recall state-of-the-art attacks, then we derive a new special-purpose attack. Our experiments show that this attack has unexpected performance and confirm that we need to study the security of special parameters sets carefully.
Funded and supported by Ecole navale, IMT Atlantique, Thales and Naval Group.
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Notes
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Computing the HNF of a matrix is not an intense computation, but can be avoided. See [SL96] for a complexity analysis.
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This work has been supported by the Chair of Naval Cyber Defense, funded by Ecole Navale, IMT-Atlantique, Thales and Naval Group.
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Bonnoron, G., Fontaine, C. (2017). A Note on Ring-LWE Security in the Case of Fully Homomorphic Encryption. In: Patra, A., Smart, N. (eds) Progress in Cryptology – INDOCRYPT 2017. INDOCRYPT 2017. Lecture Notes in Computer Science(), vol 10698. Springer, Cham. https://doi.org/10.1007/978-3-319-71667-1_2
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