  Computation offloading via device-to-device (D2D) communication, or D2D
offloading, has recently been proposed to enhance mobile computing performance
by exploiting spare computing resources of nearby user devices. The success of
D2D offloading relies on user participation in collaborative service
provisioning, which incurs extra costs to users providing the service, thus
mandating an incentive mechanism that can compensate for these costs. Although
incentive mechanism design has been intensively studied in the literature, this
paper considers a much more challenging yet less investigated problem in which
selfish users are also facing interdependent security risks, such as infectious
proximity-based attacks. Security cost is significantly different in nature
from conventional service provisioning costs such as energy consumption, since
security risks often depend on the collective behavior of all users. To this
end, we build a novel mathematical framework by leveraging the combined power
of game theory and epidemic theory to investigate the interplay between user
incentives and interdependent security risks in D2D offloading, thereby
enabling the design of security-aware incentive mechanisms. Our analysis
discovers an interesting "less is more" phenomenon: although giving users more
incentives promotes more participation, it may harm the network operator's
utility. This is because too much participation may foster persistent security
risks and as a result, the effective participation level does not improve. Our
model and analysis shed new insights on the optimization of D2D offloading
networks in the presence of interdependent security risks. Extensive
simulations are carried out to verify our analytical conclusions.
