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: ice on bridge, congestion ahead, etc Potholes Forward Collision Warning Non safety applications ◦ Traffic monitoring (with navigator) ◦ Pollution probing ◦ Pavement conditions (e.g., potholes) ◦ Content distribution ◦ Urban surveillance Primary security goals: ◦ Message integrity and authentication ◦ Detect misuse by naïve or malicious drivers. ◦ Guarantee message sender privacy

Existing Trust in Vehicle Nets Hey buddy, traffic ahead Entity Trust Are you serious? -origin integrity -data integrity Hey buddy, 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 proactive ??

Situation Aware Trust for VANETs Are you kidding? I am on a country road Hey buddy, traffic ahead Key properties: protective and predictive building of cryptographic foundation for trustworthy exchange  Proactive approach: set trust/security parameters ahead of time (secure key, unique waveform, etc)  Reduce on-line security/trust verification time  Enable security/trust in exceptional situations

How to become 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 burden is on receiver - must update private key every hour/street?? A driver wants to alert taxi of companyA on Washington Street between 10-11am that there was an accident somewhere nearby Extension 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 (have the corresponding private key) can decrypt the message

Attribute based encryption Zheng, can you please use a graphic vignette to show operation of ABE Say KSP function (KSP?) ABE like PKI, but no need for central authority, etc

8 Attributed-Based Encryption(ABE)  Encrypt Data with descriptive “Attributes”  Users Private Keys reflect Decryption Policies  Based on Identity based Encryption and Secret Sharing, not need for credentials as long as the attributed based policy is known master-key CA/PKG Authority is offline Encrypt w/attributes

9 Access Control via Situation-aware Policy Tree PK=Public Key MSK= Master Secret Key SK Sarah : “companyA” “10:30am” “Washtington St.” SK Kevin : “companyA” “10: 20 am” “Westwood” AND companyA AND amWashington St.    Sandra the sender Authority

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 amplifier In case of infrastructure failure, e.g., messenger is blocked by traffic Social network help maintain trust ◦ People gang up into communities ◦ Elected Leader is M A STER and constructs policy group (ie, Attribute Tree associated to group) ◦ Mobile users are situation aware ◦ ABE based Authenticate and encrypt Future work: ◦ How to establish social networks securely (eg 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 ◦ Handles dynamic attribute tree based on situation assessment SAT architecture components ◦ Attribute based trust ◦ Proactive trust ◦ Social trust ◦ Architecture enabling the model. Contribution to VANET: mobile proactive security for trustworthy communication! Future work: Performance Evaluation of the proposed scheme via simulation and testbed experiments

Thanks for your attention Do NOT rent a cab without SAT