What's a little collusion between friends?

This paper proposes a fundamentally different approach to addressing the challenge posed by colluding nodes to the sustainability of cooperative services. Departing from previous work that tries to address the threat by disincentivizing collusion or by modeling colluding nodes as faulty, this paper describes two new notions of equilibrium, k-indistinguishability and k-stability, that allow coalitions to leverage their associations without harming the stability of the service.