  Traffic analysis in Multi-hop Wireless Networks can expose the structure of
the network allowing attackers to focus their efforts on critical nodes. For
example, jamming the only data sink in a sensor network can cripple the
network. We propose a new communication protocol that is part of the MAC layer,
but resides conceptually between the routing layer and MAC, that is resilient
to traffic analysis. Each node broadcasts the data that it has to transmit
according to a fixed transmission schedule that is independent of the traffic
being generated, making the network immune to time correlation analysis. The
transmission pattern is identical, with the exception of a possible time shift,
at all nodes, removing spatial correlation of transmissions to network
strucutre. Data for all neighbors resides in the same encrypted packet. Each
neighbor then decides which subset of the data in a packet to forward onwards
using a routing protocol whose details are orthogonal to the proposed scheme.
We analyze the basic scheme, exploring the tradeoffs in terms of frequency of
transmission and packet size. We also explore adaptive and time changing
patterns and analyze their performance under a number of representative
scenarios.
