Access control is the process of granting permissions in accordance to an authorization policy. Mobile and ubiquitous environments challenge classical access control solutions like Role-Based Access Control. The use of context-information during policy definition and access control enforcement offers more adaptability and flexibility needed for these environments. When it comes to low-power devices, such as wireless sensor networks, access control enforcement is normally too heavy for such resourceconstrained devices. Lightweight cryptography allows encrypting the data right from its production and the access is therefore intrinsically restricted. In addition, all access control mechanisms require an authenticated user. Traditionally, user authentication is performed by means of a combination of authentication factors, statically specified in the access control policy of the authorization service. Within ubiquitous and mobile environment, there is a clear need for a flexible user authentication using the available authentication factors. In this chapter, different new techniques to ensure access control are discussed and compared to the state-of-the-art.
In the following section, the challenges of access control in ubiquitous and mobile environments are highlighted in 2 different scenarios.