SAT: Situation Aware Trust Architecture for Vehicular Networks Xiaoyan Hong, Univ of Alabama Dijiang Huang, Arizona State Univ Mario Gerla, UCLA Zhen Cao, UCLA

Vehicular Networking Apps Safe navigation: ◦ Forward collision warning ◦ Advisories to other vehicles about road perils (e.g., ice on bridge, congestion ahead) Other applications ◦ Traffic monitoring ◦ Pollution probing ◦ Pavement conditions (e.g., potholes) ◦ Urban surveil ◦ Content distribution Primary security goals: ◦ The messages is trustable ◦ Not misused by naïve drivers or malicious users. ◦ Vehicle privacy Potholes Forward Collision Warning

Trust in Vehicular Networks Hey budy, traffic ahead Entity Trust Are you serious? -origin integrity -data integrity Hey budy, traffic ahead Are you serious? -data evaluation -decision on event Data Trust Not adaptive to situation changes. Mostly a reactive approach Can we be more progressive ??

Situation Aware Trust for VANETs Are you kidding? I am in the countryside Hey budy, traffic ahead Key properties: preventive and predictive in building cryptographic foundation for trustworthy communication.  Proactive approach: set trust/security parameters ahead of time  Reduce on-line security/trust verification time  Enable security/trust in exceptional situations

How to be Situation Aware? timeplace affiliation Attribute based Trust Situation elements are encode into attributes Static attributes (affiliation) Dynamic attributes (time and place) …… Dynamic attributes can be predicted Proactive Trust establish trust in advance predict based on mobility and location service Attributes bootstrapped by social networks Social Trust Bootstrap initial trust Transitive trust relations Situation ? An attribute based situation example: Yellow Cab AND Taxi AND Seattle Street AND 10-11pm 8/22/08

Security on attribute and policy group Transportation agent: trying to alert taxi of companyA that there is an accident on Washington Street between 10-11am Extention of Attribute based Encryption (ABE) scheme [IEEE S&P 07] to incorporate dynamic access tree Attribute (companyA AND taxi AND Washington St. AND 10-11am) Extended ABE Module Ciphertext Signature plaintext Receivers who satisfy those encoded attributes (has the corresponding private key) can decrypt the message

7 Access Control via Situation-aware Policy Tree PK MSK SK Sarah : “companyA” “10:30am” “Washtington St.” SK Kevin : “companyA” “10: 20 am” “Westwood” AND companyA AND amWashington St.   

SAT Architecture: supporting situation awareness SAT Architecture: supporting situation awareness SAT layer Perception: communicate & sense environments Comprehension: extract & aggregate situations Projection: predict & create action profiles Assessment: evaluate and adjust trust situations Supporting and trust layer (STL) Security primitive Comm. primitive Portal manage

Social Trust Model How are you. People like to socialize Social trust is an incentive In case of infrastructure failure, e.g., messenger is blocked by traffic Social network will help ◦ People gang up into communities ◦ One man help construct the policy group ◦ Authenticate and encrypt the message ◦ Trust service is still available for users Two important questions ◦ How to establish social networks securely: authentication of social graph update information ◦ How to incoporate social relations to SAT: social network provides dynamic attributes in the policy tree.

Summary Situation Aware Trust Architecture ◦ Handle various situations and generate the needed security keys – location, time bounded, policy groups SAT architecture components ◦ Attribute based trust ◦ Proactive trust ◦ Social trust ◦ Architecture enabling the model. Contribution: Proactive VANET security for trustworthy communication! Future work: Evaluation of the proposed scheme via testbed experiment and simulation efforts

Thanks for your attention Do NOT rent a cab without SAT