ITIS 6010/8010: Wireless Network Security Weichao Wang

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

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)

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

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

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

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

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+2 Δ –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

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

–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

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??

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