Vehicular Public Key Infrastructure Scalability Pierpaolo Cincilla

New Threats Vehicles communicate and cooperate Context New Complexity New Applications Lane Keeping Adaptive Cruise Control Entertainment

Increasing needs for Security and Privacy Context Increasing needs for Security and Privacy Share of connected vehicles (Cisco) Security technologies in vehicles Estimated market for connected cars (McKinsey 2014)

ITS Security (ISE) Project Context Start : July 2014 3 Years ITS Security (ISE) Project Context Vehicles Broadcasts / Geocasts information to neighbor vehicle dynamics info (position, speed, heading …) perception of dynamic environment In EU, ETSI defines the PKI as the basis of trust Challenges Build security infrastructure (PKI) Ensure scalability Validation in large scale scenario llllll

Roadside ITS-S gateway Architecture ISE Architecture Overview ETSI TS 103 097, TS 102 940/941 Roadside ITS-S gateway RSU ITS Service Center EA RCA PKI AA Backbone Network 3G/4G G5 llllll

ISE PKI Architecture Architecture RCA EA AA Operator Autorization Ticket (AT) Enrollment Certificate (EC) ITS-S

Protocol EC and AT request protocol register EC AT

Centralized PKI Deployement Millions of ITSs, billions of (pseudonyms) identities We must ensure the system scalability A centralized system will saturate at some point llllll

Replicated PKI Deployement We need to distribute the system Group communication channel EA Operators AA AA WS AA WS WS ITS-S

Replicated PKI Deployement Distributed system performances Replication implications Authorization Tickets (reads) performance improve Enrollment Tickets (writes) performance worsen llllll

Replicated PKI Deployement To boost the writes…Trade consistency! Synchronous vs asynchronous updates propagation (Local vs Global) Database operation’s execution order (FIFO vs ABCAST) AA Communication channel EA Operator WS llllll

Replicated PKI Deployement Update Propagation Strong consistency: synchronous propagation Operator Register ITS EA WS ACK Communication channel

Replicated PKI Deployement Update Propagation Strong consistency: synchronous propagation Weak consistency: asynchronous propagation Operator Register ITS EA WS ACK Communication channel llllll

Replicated PKI Deployement Operation Execution Order Operators Strong consistency: Atomic Broadcast (ABCAST) Update brown ITS Register red ITS Set all SSP Register brown ITS EA WS x y z t y z x t y z x t ABCAST Communication channel y z x t llllll

Replicated PKI Deployement Operation Execution Order Operators Strong consistency: Atomic Broadcast (ABCAST) Weak consistency: First In First Out (FIFO) Update brown ITS Register red ITS Set all SSP Register brown ITS EA WS y z t x x y z t y z t x FIFO Communication channel y z x t llllll

Replicated PKI Deployement Weak consistency performances llllll

Geographic Replication EA AA IP Operator ITS-S Group Communication

Geographic Replication Big Latency IP Group Communication AA EA Operator ITS-S

10 100 IP Base case: 10 AA in US 10 AA and 10 EA in EU Group communication 10 AA in US and 10 EA in Europe Base case: 10 AA and 10 EA in EU IP Group Communication 10 100

Geographic Replication The idea: replicate EAs (and their storage) Small Latency EA EA Operator AA IP Big Latency Group Communication

Geographic Replication IP Group communication 10 AA in US and 10 EA in Europe IP Group Communication 10 AA and 10 EA in US 100 10

Geographic Replication Autorisation Ticket all settings 10 IP Group Communication 1 IP Group communication 2 IP Group Communication 3 llllll

Conclusion - Takeaway AT / EC Distributed Geographic Deployment Enrollment Cerificate weak consistency

AT Request format in SCMS EU

CAM Message Structure

DENM Message Structure

SAM Message Structure

Signed AT

US SCMS architecture

US SCMS architecture PCs provisioning steps

Certificates validity period in SCMS US.