- CAS Institute of Computing Technology
- California Institute of Technology
- Catholic University of Leuven = Katholieke Universiteit Leuven
- Center for Research in Advanced Computing Systems
- Center for Secure Information Systems [Fairfax]
- Centre National de la Recherche Scientifique
- Centre for Security, Communications and Network Research
- Chinese Academy of Sciences [Beijing]
- Chinese Academy of Sciences [Changchun Branch]