SPINS: Security Protocols for Sensor Networks Adrian Perrig et al. University of California, Berkeley Mobicom 2001 Presenter: Ryan Babbitt

Outline Background Protocols Example applications Conclusions SNEP μTESLA Example applications Authenticated Routing Node-to-node key agreement Conclusions

Background Sensor networks Nodes Base stations Communication channel Communication patterns Trust framework Resource restrictions

Security Goals for Sensor Networks Data Confidentiality Semantic security Data Authentication Point-to-point Broadcast Data Integrity Data Freshness Weak Strong

Notation

Secure Network Encryption Protocol (SNEP) Purpose: secure two-party communication Elements Symmetric key Message Authentication Code Block cipher in counter mode Shared counter

SNEP Communication Weak Version Strong Version

SNEP Implementation Key Setup Encryption Message Authentication Code Bootstrap secret master key Key generation Encryption RC5 Message Authentication Code CBC-MAC (one per packet) {M}KE, MAC(KMAC, {M}KE)

SNEP Questions What if counters lose synchronization? What if packets are lost (MAC)?

μTESLA Purpose: authenticated broadcast Phases Sender setup Broadcasting Bootstrapping receivers Receiving broadcast packets

μTESLA – Sender Side Key chain generation Broadcast Randomly pick last key Kn Repeatedly apply one-way function F Fn(Kn) <- ... <- F(F(F(Kn)) <- F(F(Kn) <- F(Kn) <- Kn K0 = F(K1) = F(F(K2) = … Broadcast Key disclosure schedule Time intervals Current key Interval offset

μTESLA – Receiver Side Bootstrapping new receivers Key commitment Loose time synchronization Key disclosure schedule Authenticating packets Check “security condition”

Applications Authenticated routing Pair-wise key agreement Build routing tree based on authenticated packets received Pair-wise key agreement

Questions What about broadcast confidentiality? What if too many keys are lost? What if a node wants to broadcast? What about group communication?

Conclusions SNEP μTESLA Scalability problems Basic node-to-base station security Susceptible to synchronization loss? Susceptible to packet loss? μTESLA Authenticated broadcast No confidentiality Scalability problems Node broadcast Pairwise/group communication

Performance