: Aurisch, T.; Steinmetz, P.

Abstract
Instant Messaging (IM) is a valuable tool for military users. It provides immediate text message exchange even when the available data transmission rate is low. We present a mechanism for connecting server based IM infrastructure to our IM application for tactical networks. The Chat and Instant Messaging for Tactical Environments (CIM-TE) application enables real-time text message exchange in tactical mobile ad hoc networks (MANETs). It provides secure group chat to a set of connected devices. No central server node is required. Some nodes, for example devices in vehicles, may be connected to an infrastructure IM server implementing the Extensible Messaging and Presence Protocol (XMPP). They connect the other CIM-TE devices to the XMPP server acting as protocol gateways. Thus, an XMPP client can join the CIM-TE group chat and instant messaging can be extended to tactical networks. Digital signatures ensure end-to-end integrity and authenticity of messages, while encryptionprovides message confidentiality. The key establishment protocol MIKE (Multicast Internet Key Exchange) provides a common encryption key for the CIM-TE nodes. If nodes join or leave the group, a new key is set automatically. The gateway functionality is the main focus of the paper.