Trustee: Full Privacy Preserving Vickrey Auction on Top of Ethereum

Abstract

The wide deployment of tokens for digital assets on top of Ethereum implies the need for powerful trading platforms. Vickrey auctions have been known to determine the real market price of items as bidders are motivated to submit their own monetary valuations without leaking their information to the competitors. Recent constructions have utilized various cryptographic protocols such as ZKP and MPC, however, these approaches either are partially privacy-preserving or require complex computations with several rounds. In this paper, we overcome these limits by presenting Trustee as a Vickrey auction on Ethereum which fully preserves bids' privacy at relatively much lower fees. Trustee consists of three components: a front-end smart contract deployed on Ethereum, an Intel SGX enclave, and a relay to redirect messages between them. Initially, the enclave generates an Ethereum account and ECDH key-pair. Subsequently, the relay publishes the account's address and ECDH public key on the smart contract. As a prerequisite, bidders are encouraged to verify the authenticity and security of Trustee by using the SGX remote attestation service. To participate in the auction, bidders utilize the ECDH public key to encrypt their bids and submit them to the smart contract. Once the bidding interval is closed, the relay retrieves the encrypted bids and feeds them to the enclave that autonomously generates a signed transaction indicating the auction winner. Finally, the relay submits the transaction to the smart contract which verifies the transaction's authenticity and the parameters' consistency before accepting the claimed auction winner. As part of our contributions, we have made a prototype for Trustee available on Github 1 for the community to review and inspect it. Additionally, we analyze the security features of Trustee and report on the transactions' gas cost incurred on Trustee smart contract.

The Security Reference Architecture for Blockchains: Toward a Standardized Model for Studying Vulnerabilities, Threats, and Defenses

“…As part of their other contribution [264], the same authors improved on high costs intrinsic to their former work [263] by using zk-SNARKs and its off-chain computation, which requires only a single on-chain proof verification of the whole auction process. However, in both approaches [263], [264], the auctioneer might compromise the privacy of all bids, which led the same authors to propose Trustee [265], Vulnerabilities, threats, and defenses of the auctions category (application layer).…”

“…Since the auctioneer of some protocols (e.g., [263], [264]) sees the bidders and their bids in plain-text, she might either intentionally or accidentally (e.g., an external compromise) leak these data (and their corresponding proofs) that are attributable to particular bidders. The protection technique is to avoid the auctioneer from seeing the plain-text of the bids, and instead use privacy-preserving integer comparison (e.g., [266]) or trusted computing-based solutions (e.g., [265]).…”

BA2P : Bidirectional and Anonymous Auction Protocol with Dispute-Freeness

“…However, these constructions are generally complex and inefficient. Galal and Youssef [27] proposed Trustee as a trusted and efficient Vickrey auction on top of Ethereum for full privacy-preservation with much lower fees for the online auction. A prototype of Trustee for the inspection and security analysis and gas costs are provided.…”

FLOCK: Fast, Lightweight, and Scalable Allocation for Decentralized Services on Blockchain

“…Galal and Youssef propose a number of sealed bid auctions [17], [18]. Most recently, Trustee [19] presents a Vickrey auction on Ethereum using TEEs. The smart contract is used as a billboard, after which computation is transferred to an enclave using a relay controlled by an auctioneer.…”