Identity-Based cryptography has been proposed in mobile ad-hoc networks (MANETs) to provide security. However, the figure of the Private Key Generator (PKG) is not adequate in the MANET setting, since it may not be reachable by all nodes, can fail during the life-time of the protocol or can even be attacked, compromising the whole system. Previous works distribute the task of the PKG among a set of nodes by means of a secret sharing scheme. In this paper we propose an efficient solution to emulate in a dynamic and distributed way the role of the PKG in so that even new nodes joining the network are able to issue shares of the master key of an Identity- Based scheme. In this way, the distributed PKG spreads dynamically among the nodes as the network increases. Furthermore, the techniques we propose may be suitable for other protocols over MANETs.

Vanesa Daza is partly supported by the Catalan Government under grant 2005 SGR 00446, and by the Spanish Ministry of Science and Education through project SEG2004-04352-C04-01 “PROPRIETAS”. Paz Morillo and Carla Ràfols are supported by Spanish Ministry of Science and Education through project TIC 2003- 00866.