We consider the sale of a single item to multiple buyers by a revenue-maximizing seller. Informally, an auction is credible if the auctioneer themselves is incentivized to execute the auction in earnest, even when permitted to cheat in ways that are undetectable to the bidders. Recent work by Akbarpour and Li prove that the only optimal, credible, strategyproof auction is the ascending price auction which requires unbounded communication.
In contrast, we show that the mild additional assumption of a cryptographically secure commitment scheme suffices for a simple two-round auction which is optimal, credible, and strategyproof for a large class of distributions over buyer valuations.