We study optimal bidder collusion at first-price auctions when the collusive mechanism only relies on signals about bidders' valuations. We build on Fang and Morris (2006) when two bidders have low or high private valuation of a single object and additionally each receives a private noisy signal...

We present an extension to any finite complete information game with two players. In the extension, players are allowed to communicate directly and, additionally, send private messages to a simple, detail-free mediator, which, in turn, makes public announcements as a deterministic function of...

We show how to bid in first-price auctions when a bidder knows her own value but not how others will bid. To do this we introduce a novel and general method for how to make choices in strategic settings without assuming common knowledge or equilibrium behavior. Accordingly, first eliminate...