  While network coding can be an efficient means of information dissemination
in networks, it is highly susceptible to "pollution attacks," as the injection
of even a single erroneous packet has the potential to corrupt each and every
packet received by a given destination. Even when suitable error-control coding
is applied, an adversary can, in many interesting practical situations,
overwhelm the error-correcting capability of the code. To limit the power of
potential adversaries, a broadcast transformation is introduced, in which nodes
are limited to just a single (broadcast) transmission per generation. Under
this broadcast transformation, the multicast capacity of a network is changed
(in general reduced) from the number of edge-disjoint paths between source and
sink to the number of internally-disjoint paths. Exploiting this fact, we
propose a family of networks whose capacity is largely unaffected by a
broadcast transformation. This results in a significant achievable transmission
rate for such networks, even in the presence of adversaries.
