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

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

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

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

5. Notation

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

7. SNEP Communication
Weak Version
Strong Version

8. 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)

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

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

11. 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

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

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

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

15. 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

16. Performance