Jean-Paul Delahaye is Professor Emeritus at the University of Lille and a researcher at the CRISTAL laboratory (Centre de recherche en informatique signal et automatique de Lille, UMR CNRS 9189). His work focuses on sequence transformation algorithms (Thesis), on the use of logic in Artificial Intelligence (expert systems, Prolog language), on the computational theory of games (iterated games, simulation of social systems, study of cooperation), and on algorithmic information theory (Kolmogorov complexity theory, computational centent) with applications to bioinformatics and finance. He is currently working on cryptographic currencies and "blockchain technology". He is also interested in ethical problems in science and is a member of the Comité d'éthique du CNRS (COMETS). He has supervised 20 theses. He is the author 22 books, some of which are intended for a wide public. In 1998, he received the Prix d'Alembert from the Société Mathématique de France and, in 1999, the Prix Auteur de la Culture scientifique from the Ministry of National Education and Research. He writes the monthly column Logique et calcul (6 pages) in the journal Pour la science (French version of Scientific American). He also runs a blog (http://www.scilogs.fr/complexites/) dedicated to "Complexities".