[HGI-News] HGI-Seminar, Donnerstag 4.05.06: On security model for group key exchange protocols

[Newsletter des Horst Görtz Instituts]

                        Dr. Emmanuel Bresson
         Cryptology department, CELAR Technology Center, France

             Donnerstag 4. Mai 2006, 13:30 Uhr IC 4 / 39-41
                       (Vortrag auf Englisch)

           On security model for group key exchange protocols

A group key exchange protocol enable a pool of participants, communicating
over a public network, to securely establish a common session key, in such
a way that nobody outside the pool get information about it. While key
exhange is a central primitive in cryptography, the formalization of the
underlying security notions, as well as those required in the case of
group key exchange, has been achieved only quite recently.

In this talk, we describe the formal security model we have proposed in
2001 (joint work with O. Chevassut and D. Pointcheval) in order to analyze
existing protocols, for which only heuristic security arguments had been
given. We will discuss in details the extensions and refinements that can
be made to this model: formalizing authentication between the players,
dealing with concurrent executions, corruption and forward-secrecy,
dynamicity of group membership, etc. We will also compare the model with
other approaches that have been developped by Bellare, Canetti et al., and
we will briefly discuss the possible variants of the model, in particular
how to enhance it in order to deal with password-based scenarios.


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