Cryptobazaar: Private Sealed-bid Auctions at Scale

This work introduces Cryptobazaar, a scalable, private, and decentralized sealed-bid auction protocol. In particular, our protocol protects the privacy of losing bidders by preserving the confidentiality of their bids while ensuring public verifiability of the outcome and relying only on a single untrusted auctioneer for coordination. At its core, Cryptobazaar combines an efficient distributed protocol to compute the logical-OR for a list of unary-encoded bids with various novel zero-knowledge succinct arguments of knowledge that may be of independent interest. We present protocol variants that can be used for efficient first-, second-, and more generally (p + 1)st-price as well as sequential first-price auctions. Finally, the performance evaluation of our Cryptobazaar implementation shows that it is highly practical. For example, a single auction run with 128 bidders and a price range of 1024 values terminates in less than 0.5 sec and requires each bidder to send and receive only about 32 KB of data. * Andrija Novakovic and Alireza Kavousi jointly led the research and contributed equally to this work.