  The distributed computation of a Nash equilibrium in aggregative games is
gaining increased traction in recent years. Of particular interest is the
mediator-free scenario where individual players only access or observe the
decisions of their neighbors due to practical constraints. Given the
competitive rivalry among participating players, protecting the privacy of
individual players becomes imperative when sensitive information is involved.
We propose a fully distributed equilibrium-computation approach for aggregative
games that can achieve both rigorous differential privacy and guaranteed
computation accuracy of the Nash equilibrium. This is in sharp contrast to
existing differential-privacy solutions for aggregative games that have to
either sacrifice the accuracy of equilibrium computation to gain rigorous
privacy guarantees, or allow the cumulative privacy budget to grow unbounded,
hence losing privacy guarantees, as iteration proceeds. Our approach uses
independent noises across players, thus making it effective even when
adversaries have access to all shared messages as well as the underlying
algorithm structure. The encryption-free nature of the proposed approach, also
ensures efficiency in computation and communication. The approach is also
applicable in stochastic aggregative games, able to ensure both rigorous
differential privacy and guaranteed computation accuracy of the Nash
equilibrium when individual players only have stochastic estimates of their
pseudo-gradient mappings. Numerical comparisons with existing counterparts
confirm the effectiveness of the proposed approach.
