Sensor networks consist of a potentially huge number of very small and resource limited self-organizing devices. Those devices offer different services and use services provided by other sensor nodes. To give sensor nodes the possibility to offer services and to network-wide search for available services, some kind of lookup facility is needed. Several possibilities exist to realize service lookup in traditional networks and ad-hoc networks. In this paper we present Secure Content Addressable Networks Version 2 (SCANv2), a secure overlay focusing especially on wireless sensor networks. The paper describes how this secure overlay can be used among other things to offer lookup functionality in sensor networks. The design of the overlay focuses on secure service lookups. The overlay is part of the Karlsruhe Sensor Network Platform K-SNeP, a modular and flexible architecture for service centric sensor networks. Key areas of application of the architecture are gradually extendable service centric sensor networks where sensors and actuators jointly perform various user defined tasks, e.g. in the field of an office environment or health care.