[Resource Topic] 2003/171: Scalable Protocols for Authenticated Group Key Exchange

Welcome to the resource topic for 2003/171

Scalable Protocols for Authenticated Group Key Exchange

Authors: Jonathan Katz, Moti Yung


We consider the fundamental problem of authenticated group key
exchange among n parties within a larger and insecure public
network. A number of solutions to this problem have been proposed;
however, all provably-secure solutions thus far are not scalable and,
in particular, require O(n) rounds. Our main contribution is the
first {\em scalable} protocol for this problem along with a rigorous
proof of security in the standard model under the DDH assumption;
our protocol uses a constant number of rounds and requires only O(1)
``full’’ modular exponentiations per user. Toward this goal and of
independent interest, we first present a scalable compiler that
transforms any group key-exchange protocol secure against a passive
eavesdropper to an \emph{authenticated} protocol which is secure
against an active adversary who controls all communication in the
network. This compiler adds only one round and O(1) communication
(per user) to the original scheme. We then prove secure — against a
passive adversary — a variant of the two-round group key-exchange
protocol of Burmester and Desmedt. Applying our compiler to this
protocol results in a provably-secure three-round protocol for
\emph{authenticated} group key exchange which also achieves
forward secrecy.

ePrint: https://eprint.iacr.org/2003/171

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