Smart spaces enable heterogeneous devices to cooperate dynamically in various environments. They can be used, for instance, in personal, home, office or public networks to share information between devices ranging from sensors and embedded gadgets to PCs, servers, mobile phones and entertainment electronics. However, before smart spaces can be used in multi-user environments they must provide feasible solutions for access control and privacy as well as for authenticity and confidentiality of communication. In this paper, we will describe security and access control mechanisms within our own implementation of Semantic Information Broker, RIBS