# Exercise Sheet 3

```Security and Cooperation in Wireless
Networks
Exercise Sheet 3
WS 12/13
Telematics Group,
University of Goettingen,
[email protected]
December 21, 2012
A. Securing Neighbor Discovery
(1) The statistical wormhole detection method detects the presence of a wormhole with high
confidence. However, it does not locate it. How can the nodes that are affected by the wormhole
be identified?
(2) Let us consider the TIK protocol. Assume that the maximum clock synchronization error is 180
ns and the maximum communication range of the nodes is 250 m. Compute the minimum packet
duration required by the TIK protocol in order for the TESLA condition to be satisfied. Deduce
the minimum Packet length if the bit rate is 10 Mbits/s.
(3) Consider the wormhole detection method based on directional antennas using a verifier. Try to
construct an example with two wormholes that are not detected by the described method.
B. Secure Routing in Multi-hop Wireless Networks
(1) Routing Protocols:
a. What are the different types of routing protocols? Describe them briefly.
b. An Ad hoc network is formed by sensor nodes moving in a continuous random manner
such that the network topology is always changing. The sensor nodes transmit data only
upon a change of the sensed information to a node multi-hops away acting as the sink.
Otherwise, they keep in sleep mode to save power. Which kind of routing protocols
would better suite this network? Explain why. (Note: no localization information
available).
c. Consider now an Ad hoc network with very low mobility, where the nodes transfer timecritical data continuously. What kind of routing protocols would better suite this
network? Explain why. (Note: no localization information available)
(2) What is the major difference between AODV and DSR routing protocols?
(3) Consider the following network (Links are bidirectional):
a. Assume that the network uses dynamic source routing (DSR) as the routing algorithm.
i.
Node 1 wants to send data to node 13. Perform the DSR algorithm on the network (write
down all messages transmitted). What information will node 1 get and how does it get it?
b. Assume the network uses Ad Hoc On Demand Distance Vector (AODV) as the routing
algorithm.
i.
Node 1 wants to send data to node 13. Perform the AODV algorithm on the network
(write down all messages transmitted). What information will node 1 get and how does it
get it?
ii.
What information do nodes, on the path between node 1 and 13, need to store in their
routing table?
iii.
Consider now an attacker in range of nodes 2, 4, 5 transmitting incorrect routing
information. How can the attacker create a routing loop? Show the RREP packets that
need to be transmitted.
(4) Consider the following network where A1 and A2 are colluding attackers:
1
Describe an attack mounted by the colluding attackers against the SRP routing protocol such that S
receives the route (S, F1, A1, G1, Gn, A2, F2, D) while G1 and Gn are not neighbors.
(5) What are the disadvantages (or constraints) of using Ariadne routing protocol with:
 Digital signatures,
 Standard MACs,
 TESLA
(6) How is the SAODV routing protocol vulnerable to an attacker on the route path? Give an
example.
(7) What particularities of WSNs (Wireless Sensor Networks) should be considered in developing a
secure routing protocol?
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