In a group key exchange protocol, a group of players must compute a common secret key by using only public channels. There
are many proposed protocols for group key exchange, and all of them are balanced or symmetric: all the players must perform
the same amount of computation in the protocol.
We propose an unbalanced group key exchange scheme: two of the players perform most of the computations of the protocol. This
scheme can be useful in situations where players do not all have the same computational and communication resources. The security
of the protocol is based on the Decisional Diffie-Hellman Assumption.
This work was partially supported by Spanish Ministerio de Ciencia y Tecnología under project TIC 2003-00866.