Hans van Ditmarsch is a senior researcher at CNRS (the French National Research Organization), and based at LORIA in Nancy, where he is heading the research team CELLO (Computational Epistemic Logic in LOrraine). He is also affiliated to IMSc (Institute for Mathematical Sciences), in Chennai. He is the recipient of an ERC (European Research Council) starting grant Epistemic Protocol Synthesis. He has previously been based at the Open University of the Netherlands, the University of Groningen, the University of Otago, and the University of Sevilla. His PhD is from the University of Groningen. His research is on the dynamics of knowledge and belief, information-based security protocols, modal logics, and combinatorics. He has frequently taught at ESSLLI summer schools, and he was an organizer or chair of events such as LOFT, M4M, ESSLLI, Tools for Teaching Logic, and LORI. He has been an editor of the Journal of Philosophical Logic. He is an author of the textbook and monograph Dynamic Epistemic Logic, an editor of the Handbook of Epistemic Logic, and an author of the logic puzzles book One Hundred Prisoners and a Light Bulb. January 2018 to June 2018 he was based at ReLaX, Research Lab in Computer Science, Indo-French Research Unit, CNRS UMI 2000. ReLaX is located in Chennai, India.