by Mattias Johansson, Gunnar Kreitz, Fredrik Lindholm.

Published in LNCS 3989 (pp. 178-193), Proceedings of ACNS 2006

This paper describes a method to convert stateless key revocation schemes based on the subset cover principle into stateful schemes. The main motivation is to reduce the bandwidth overhead to make broadcast encryption schemes more practical in network environments with limited bandwidth resources, such as cellular networks. This modification is not fully collusion-resistant.

A concrete new scheme based on the Subset Difference scheme is
presented, accomplishing a bandwidth overhead of *Δm + 2
Δr + 1* compared to e.g. Logical Key Hierarchy's
*2(Δm + Δr)*log *m*, where *Δm*
and *Δr* is the number of members added and removed since
the last stateful update and *m* is the number of current
members.

**Keywords.** Broadcast encryption, key revocation,
subset cover, Subset Difference, Logical Key Hierarchy, stateful,
stateless.

- Slides from presentation at ACNS 2006
- Full Article