A key feature of ubiquitous handheld devices will be their simple usability in mobile and highly dynamic, ad-hoc peer-to-peer environments. With LINDA, JAVASPACES and TSPACES, shared memory-based communication concepts have been realized on the system level with corresponding APIs. This work proposes to use the same simple communication paradigm consistently on the user interface level. In addition the InfoSpace idea shall be completed with a security system. This security system is very generic and can be adapted to and implemented in actual peer to peer systems, which have as their main goal to exchange object and which support virtual rooms (InfoSpaces). Furthermore the user will work with simple access control matrices, which are converted to keys by the lower protocol layers. The main goal is to demonstrate a security system for dynamic ad-hoc P2P systems, without relying on servers or clients with master functionality.