We consider a multiple access relay network where
multiple sources send independent data to a single destination
through multiple relays, which may inject falsified data into the
network. To detect the malicious relays and discard (erase) data
from them, tracing bits are embedded in the information data at
each source node. In addition, parity bits are added to correct
the errors caused by fading and noise. When the total amount of
redundancy, tracing bits plus parity bits, is fixed, an increase in
parity bits to increase the reliability requires a decrease in tracing
bits, which leads to a less accurate detection of malicious behavior
of relays, and vice versa. We investigate the tradeoff between the
tracing bits and the parity bits in minimizing the probability of
decoding error and maximizing the throughput in multisource,
multirelay networks under falsified data injection attacks. The
energy and throughput gains provided by the optimal allocation
of redundancy and the tradeoff between reliability and security
are analyzed.