Building an Onchain Confidential Single-Price Auction for Token Sales with Sealed Bids using Zama's fhEVM

Zama's fhEVM bounty program in Season 7 focused on creating a smart contract system for a Single-Price Auction (SPA) using Solidity, where bids are sealed to maintain confidentiality. The challenge required developers to design a system that balances privacy and scalability, with the settlement price determined by the lowest price among winning bids. The winning submission by Palra introduced innovative design choices, including a custom Solidity library called HalfEncryptedFenwickTree, which efficiently processes bids while maintaining partial confidentiality by encrypting quantities but not prices. This approach leverages a Fenwick tree data structure for efficient auction operations and introduces a customized decryption scheme for settlement. Despite the challenge's complexity, the submission effectively addresses scalability issues and offers a promising proof-of-concept for privacy-centric auctions on the Ethereum Virtual Machine (EVM), though it remains unaudited and carries inherent risks associated with smart contracts.