Secure communication within a large group of users such as
participants in a phone or video conference relies on the availability of
secure data and efficient data transmission. Group key exchange protocols
allow a (large) group of n users to establish a joint secret key which
can be used in symmetric systems to efficiently en- and decrypt messages
to and from the group. To deal with varying constellations of the groups
and to ensure key freshness it is essential that the group key exchange
protocol is efficient.
Most protocols are generalizations of two-party protocols like Diffie-
Hellman key exchange. The Burmester and Desmedt I protocol establishes
a key in a constant number of rounds independent of the size of
the group of users and in O(n) complexity of computation per user.
After Joux’s proposal to use pairings to enable a one-round tripartite
key exchange (KE) several extensions of existing group KE and authenticated
key exchange (AKE) protocols were published. However, quite
a few turned out to be flawed and the complexity is often worse than
for the original scheme. In this paper we propose a new constant round
pairing based group AKE protocol which requires a lower computational
complexity per user compared to previous proposals. Furthermore, the
scheme is particularly interesting for groups in which some members enjoy
more computational power than others. The protocol is most efficient
if these members constitute roughly half of the group.
We also provide a pairing-based version of the Burmester-Desmedt II
group key exchange which runs in 3 rounds and requires only O(log n)
computation and communication.
Both protocols are faster than any published pairing-based key exchange
protocols. If the parameters are chosen appropriately so that the
pairing computations are fast the protocols can outperform the respective
DL-based Burmester-Desmedt key exchange protocols.
|Title of host publication||Financial Cryptography and Data Security (12th International Conference, FC 2008, Cozumel, Mexico, January 28-31, 2008, Revised Selected Papers)|
|Place of Publication||Berlin|
|Publication status||Published - 2008|
|Name||Lecture Notes in Computer Science|