Private Sealed-bid Auctions at Scale

Abstract: The growing use of auctions in blockchain and decentralized systems raises a central challenge: how can auction outcomes be computed efficiently and verified publicly without exposing bids or trusting an auctioneer? This talk explores recent results and cryptographic techniques for private sealed-bid auctions, highlighting the trade-offs between privacy, scalability, and trust assumptions, particularly when losing bids must remain confidential after an auction concludes.

The talk then presents Cryptobazaar (NDSS 2026), a system that combines lightweight distributed computing with succinct zero-knowledge proofs to enable publicly verifiable auctions coordinated by a single untrusted auctioneer. It discusses how the design supports different auction modes, the security implications, and considerations for deploying private auctions on a large scale.

Joint work: Kobi Gurkan, Philipp Jovanovic, Alireza Kavousi, Andrija Novakovic, István András Seres.

Suggested readings

• Cryptobazaar: Private Sealed-bid Auctions at Scale (ia.cr/2024/1410)
• Rust Implementation of Cryptobazaar (GitHub repository)
• Homomorphic Signature-based Witness Encryption and Applications (ia.cr/2025/443)