The broadcast nature of the communication channel
enables a malicious eavesdropper to gain information about
connectivity and active sessions in a multi-hop wireless network.
This can be achieved simply by overhearing the transmitted
signals over the ether and analyzing their timings. Focusing
on techniques that can meet information-theoretic criteria for
session anonymity under traffic analysis attacks, we rely on a
judicious choice of transmission schedules to conceal multicast
or bidirectional unicast sessions from a global eavesdropper at
any given point in time. A systematic approach for constructing
the aforementioned transmission schedules for arbitrary network
topologies is derived from an equivalent coloring problem in
an auxiliary conflict graph. Although this type of anonymity
requires various nodes to send dummy transmissions to confuse
the eavesdropper, our results show that the additional cost in
terms of energy, delay and throughput can be alleviated using
network coding. The key intuition is that dummy transmissions
can be replaced by coded transmissions, which carry useful
information. For the case of a line network with N nodes
supporting coded flows, we derive closed-form expressions, which
show that anonymity comes at no cost in terms of throughput
if at least one of the destinations is two hops away. The average
per packet delay is shown to increase by at most 50%.