ITIS 6010/8010: Wireless Network Security

1. ITIS 6010/8010: Wireless Network Security Weichao Wang

2. Secure Efficient Ad Hoc Distance Vector (SEAD) • Is based on DSDV • Use hash chain to accomplish authentication and avoid DoS • Assumptions: • The diameter of the network is shorter than m hops • Use hash chains to authenticate route updates • The hash results are used in groups of m • New hash chains can be generated when old ones are finished

3. Very similar to SAODV: use hash chain to make sure a malicious node cannot decrement the distance vector • Use sequence number to determine which group of hash values will be used for authentication • Example • Node S generates a hash chain with length 1000, and network diameter is m. for sequence i, k = (1000 / m) – i, the node will use hash value h(km) to h(km+m-1)

4. In this way, we prevent the fake sequence number • A node will verify the hash value before updating its routing table. It hashes again to match the increased distance metric. • Why we try to reduce digital signature • Too much computation overhead • Can be used to conduct DOS attack

5. Advantage over SAODV • SAODV uses digital signature to protect the sequence number, but SEAD binds sequence number, hop metric, and hash chain together • We do not need to sign the final hash result every time • Performance comparison to DSDV • Higher delivery ratio but longer delay • Higher packet and byte overhead

7. Ariadne: • On-demand protocol based on DSR • Based on TESLA to authenticate packets • Need loosely synchronized clocks

8. Intro of TESLA • Is a broadcast authentication protocol • Depend on clock synchronization and delayed disclosure • Every node generates a hash chain, and the previous hash value can be used to authenticate the later values • The node discloses the hash result at a determined interval • Use a not-published-yet hash value as key for symmetric encryption or MAC • The receivers can authenticate the packet later when the key is disclosed

9. Example • The clock synchronization error is Δ, longest end-to-end delay is t, node S will chose a key that will not be disclosed until t+2Δ • The receiver will examine the key and make sure that it has not been disclosed. Otherwise, the packet can be generated by an attacker • The receiver buffers the packet until the key is disclosed to authenticate the packet

10. Basic Ariadne Route Discovery • Node S wants to locate a path to D, A to C in the middle • Want to enforce three features • S and D can authenticate each other • Both S and D can authenticate the intermediate nodes (maybe only one of S and D) • No intermediate node is missing

11. Both pairwise keys and TESLA keys are used • S and D authenticate each other with pairwise key • The intermediate nodes can be authenticated by • TESLA keys with delayed disclosure, but S has to trust D to authenticate all intermediate nodes • Every intermediate node signs the route request • Pair wise key between D and the intermediate nodes • Per-hop hashing to make sure no node is removed • Example: Ariadne using TESLA

15. Route Error with TESLA • A node C finds that the link CD breaks, so it sends a route error back to S with TESLA key authentication. This path will be used until delayed authentication is confirmed. (hint: TESLA uses delayed disclosure and authentication) • Question: if we already have pairwise keys, what is the advantage of using TESLA??

16. Summary • WatchDog + PathFinder: DSR • SAODV: Digital signature + Hash chain, AODV • SEAD: Hash chain, DSDV • Ariadne: Pairwise key + hash chain + delayed disclosure, DSR