Universiteit Leiden

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Computational aspects of class group actions and applications to post-quantum cryptography

Most of current public-key cryptography is considered insecure against attacks from sufficiently powerful quantum computers. Post-quantum cryptography studies methods to secure information resistant against such attacks. One proposal is isogeny-based cryptography, which bases its security on computational hardness assumptions related to maps between elliptic curves.

M.R. Houben
28 February 2024
Thesis in Leiden Repository

We analyze the security of isogeny-based cryptographic schemes, in particular those based on class group actions. We find special cases in which the underlying computational hardness assumptions can be broken, sometimes even by classical computers. Furthermore, we study a method, known as radical isogenies, to accelerate the execution of isogeny-based protocols. Finally, we introduce multivariate generalizations of Hilbert class polynomials, which may yield computational benefits compared to their univariate counterparts.

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