We developed a new approach and designed a practical solution for securing communication of dynamic groups in dynamic network-centric environments, such as airborne and terrestrial on-the-move networks. The solution is called Public Key Group Encryption (PKGE). In this paper, we define the problem of group encryption, motivate the need for decentralized group encryption services, and explain our vision for designing such services. We then describe our solution, PKGE, at a high-level, and report on the prototype implementation, performance experiments, and a demonstration with GAIM/Jabber chat.