Persistent Authentication in Smart Environments

Inhabitants in smart environments are often authenticated when they enter the smart environment, e.g., through biometrics or smart-/swipe-card systems. It may sometimes be necessary to re-authenticate when an inhabitant wishes to enter a restricted area or access ambient services or location based information, e.g., it is common to have swipe card terminals placed next to doors to restricted areas. This means that all access to protected resources must have individual means of authenticating users, which makes the access control system more expensive and less flexible, because access controls will not be installed unless it is absolutely necessary. The cost of installing and maintaining an authentication infrastructure and the inconvenience of repeatedly authenticating toward different location based service providers mean that new models of authentication are needed in smart environments. This paper defines a persistent authentication model for a smart environment, which tracks inhabitants in the smart environment from the point of authentication to the protected resource, thus rendering authentication persistent by correlating the initial authentication event with the access control request. We present a proof-of-concept implementation of the proposed mechanism, which employs camera based tracking with a single stationary 3D camera that uses the "time of flight" principle. A preliminary evaluation of the proposed mechanism indicates that persistent authentication is technically possible with the proposed hardware. The proposed model is sufficiently general to allow the addition of more cameras or supplemental tracking technologies, which will improve the robustness and scalability of the proposed mechanism.