Serverless distributed computing, especially Mobile Ad-hoc NETworks (MANETs) have received significant attention from the research community. Peer-to-peer overlay networks have the potential to accommodate large-scale, decentralised applications that can be integrated into a MANET architecture to enable peer-to-peer communication among different mobile peers. These overlay architectures must be very resilient and their utilisation, reliability and availability must satisfy the needs of mobile computing. One must also heed the fact that the wireless nature of the medium introduces security vulnerabilities. The aim of the work described in this paper is twofold. First, we describe our peer-to-peer distributed hash table (DHT) architecture entitled Reliable Overlay Based Utilisation of Services and Topology (ROBUST). This is designed to be efficiently applied to MANETs. We additionally propose security extensions to protect the ROBUST signalling messages against malicious activities. We evaluate the ROBUST performance as well as the security extensions under varying levels of mobility and network sizes by building a custom DHT module for the network simulator ns-2. The outcome of the results show negligible overhead introduced by the extensions giving credence to their application in security sensitive scenarios.