Alexandre Gélin

Mathematics Teacher
PhD in Computer Science
Research Associate at LMV

alexandre.gelin (at)


Laboratoire de Mathématiques de Versailles
Université de Versailles-St-Quentin-en-Yvelines
Université Paris-Saclay — CNRS
45 avenue des États-Unis, 78035 VERSAILLES

About me

From September 2020, I am a Math Teacher in French Preparatory Classes in Normandy.

In the meantime, I remain involved in research as a Research Associate in the Crypto team at the Laboratoire de Mathématiques de Versailles (LMV).


My research topic is at the boundary between mathematics and computer science. Particularly, I am interested in algebraic structures that are suitable for cryptographic purposes. Class groups of number fields are among the structures I work on. Computing efficiently their cardinality as well as the structure of such groups are hard problems in practice.

These groups naturally provide applications in cryptology, because they are finite groups. Actually, an important proportion of current public-key cryptosystems relies on the use of discrete exponentiation in a finite group, because the inverse operation is considered difficult: this is the so-called discrete logarithm problem.

I am also interested in other connected topics, linked for most of them to public-key cryptography: elliptic or higher genus curves or factorization for instance.