In this paper, we propose some cryptographic techniques to securely set up a mobile ad-hoc network. The process is fully self-managed by the nodes, without any trusted party. New nodes can join the network and are able to obtain the same capabilities as initial nodes; further, each node can obtain a pair of secret/public keys to secure and authenticate its communication. Two additional features of our system are that it allows to implement threshold operations (signature or decryption) involving subgroups of nodes in the network and that any subgroup with a small number of nodes (between 2 and 6) can obtain a common secret key without any communication after the set up phase. Ó 2007 Elsevier B.V. All rights reserved.