Kai Rannenberg holds the T-Mobile Chair of Mobile Business & Multilateral Security since 2002. Before he was with the System Security Group at Microsoft Research Cambridge, UK focusing on "Personal Security Devices & Privacy Technologies".

1993-1999 Kai worked at Freiburg University and coordinated the interdisciplinary "Kolleg Security in Communication Technology", sponsored by Gottlieb Daimler & Karl Benz Foundation researching Multilateral Security. After a Diploma in Informatics at TU Berlin he had focused his PhD at Freiburg University on IT Security Evaluation Criteria and their potential and limits regarding the protection of users and subscribers. Since 1991 Kai is active in the ISO/IEC standardization of IT Security and Criteria (JTC 1/SC 27/WG 3 Security evaluation criteria). Since March 2007 he is Convenor of the SC 27/WG 5 Identity management and privacy technologies.

Since May 2007 Kai chairs IFIP TC-11 Security and Privacy Protection in Information Processing Systems, after having been its Vice-Chair since 2001. Kai is active in the Council of European Professional Informatics Societies (CEPIS) chairing its Legal & Security Issues Special Interest Network (CEPIS LSI) since 2003.

In July 2004 Kai was appointed as the academic expert to the Management Board of the European Network and Information Security Agency, ENISA. Kai`s awards include the IFIP Silver Core, the Alcatel SEL Foundation Dissertation Award and the Friedrich-August-von-Hayek-Preis of Freiburg University and Deutsche Bank.