New dynamic group key agreement protocols and their formal analysis and applications

Abstract

The essence of dynamic group key agreement protocols is to help compute a secure key for a group communication with a dynamic set of participants in distributed systems. Dynamic group key agreement protocols are expected to be used in applications such as conference communications, file sharing systems and mobile ad hoc networks. In dynamic group key agreement protocols, the number of participants may vary in time because of participants are joining or leaving a group. The security of such operations is affected by the existence of backward confidentiality and forward confidentiality, respectively. There are a number of problems related to the use of existing dynamic group key agreement protocols: (i) inefficient fault detection in conference communications, (ii) lack of privacy, violation of availability, inefficient participant revocation, dependency for key escrow in file sharing systems and (iii) insecure cluster head selection in mobile ad hoc networks. In this thesis, we first introduce an improved Dynamic Conference Key Agreement Protocol with dynamic group capabilities to provide better performance in fault detection and correction. Then, we show the application of the proposed protocol on Three-Tier Secure File Sharing System with efficient participant revocation. Second, we propose another Key Agreement Protocol with Partial Backward Confidentiality. The partial backward confidentiality property is a novel security property that allows a new participant to compute the last valid group key just before joining the group. In relation to this protocol, we propose a Private File Sharing System. Third, we propose a Group Key Agreement Protocol for Mobile Ad hoc Networks. In this protocol, we introduce the new concept of secure cluster head selection.