Philip Robinson & Michael Beigl Telecooperation Office University of Karlsruhe

1. Trust Context Spacesan Architecture for Security in Pervasive ComputingSPC 2003, Boppard Germany, 13.03.2003 Philip Robinson & Michael Beigl Telecooperation Office University of Karlsruhe

2. Key Terms “just to put things in context” • Context • Interactive Context • Security Context • Trust Context

3. Context • … any information that can be used to characterize the situation of an entity, where an entity can be a person, place, or physical or computational object. (Abowd, Dey, 1999) Application (Computational) Context Physical Context

4. Interactive Context • any information that characterizes the state of an interaction (more than one entity), including the identites involved, relationships formed (sessions established), accessible data and operations. Physical Physical Application (Computational) Application (Computational)

5. Security Context • any information that characterizes the policies and mechanisms used to meet the protection requirements, and hence safeguard the current interactive context Physical Physical Application (Computational) Application (Computational)

6. Trust Context • any information that can be used to characterize the evidence and assurances that the security context for a particular interactive context is and will be maintained. Physical Physical Application (Computational) Application (Computational)

7. What has changed in Pervasive Computing? Greater overlap of physical and virtual environments • Networked Sensor technology led to Augmented Reality • Physical actions and changes in the environment have more significance in computer applications (Context-Awareness) • Virtual events have more real-world significance, without obtrusion (Ambient Technologies) • The interactive context has been widened Application (Computational) Context Physical Context

8. What has changed in Pervasive Computing? Each sector represents the scope of identities, sessions, accessibility of data and operations The implicitly shared interactive context has been widened Personal Interactive Context Implictly Shared Interactive Context Explictly Shared Interactive Context Public Interactive Context

9. but may result in...

10. termination interaction W2 session (secure channel) trust decision W1 discovery Security Vulnerability Windows physical virtual Value of Context Information Time (t)

11. Goals of Trust Context Spaces Minimize occurences of Security Vulnerability Windows Control the security risks associated with implicitly shared information

12. Principle 1Equilibrium of Physical and Virtual Security • Perception: physical cues for security translated into invocation of virtual security mechanisms • Actuation: virtual security-related events produce active notification or adaptation of physical environment

13. Principle 2:Trust in the Environment • Some trust decisions are offloaded to the environment‘s security services (natural behavior) • Environment = rooms, offices, buildings etc. A definite space • A Trust Context Space therefore has both physical and virtual properties; implying both physical and virtual identities, assets, operations, and relationships

14. Principle 3Shared Unique Context as a Basis for Security • A good secret key must not be repeatable or easily derived • Efforts to facilitate yet secure implicit interaction • The more parties interact, the more unique their shared context becomes (cumulative trust)

15. Architecture

16. Scenario

17. Conclusion – Contributions & Evaluation • Incubation of virtual identities/ counterparts within Controlled spaces (meeting rooms, offices...) • Public Trust Context Spaces are further challenge • Entropy of context information has to be taken into consideration, if being used for implicit key generation