We propose two different approaches to implement the peer-to-peer (P2P) version of the Session Initiation Protocol (SIP) in mobile ad hoc networks (MANETs), focusing on private (e.g. military) networks. Both inspired by state-of-the-art approaches, one uses a flooding-based name resolution mechanism while the other instead makes use of a distributed hash table (DHT). We then provide a security solution built on top of both approaches using an offline public key infrastructure (PKI) and redundancy to ensure data integrity and availability. This is similar to one existing solution in particular - the RELOAD standard - but we also tackle issues that affect it notably by being careful with the redundancy scheme. We then present results from performing experiments in a simulator for both of our approaches, demonstrating that they do not suffer from some of the issues affecting other state-of-the-art solutions including RELOAD.