Flashbots Makes Privacy-Enhanced Block Builder Open Source on Ethereum Testnet Sepolia

Research shared by the team details that block builders will be able to build blocks without accessing private data of users' transactions.

AccessTimeIconMar 3, 2023 at 3:55 p.m. UTC
Updated Mar 3, 2023 at 4:22 p.m. UTC

Flashbots, an Ethereum research and development firm, has made open source a new block builder operating in a trusted environment, in this case a private mempool, on Ethereum’s Sepolia testnet, according to a press release shared exclusively with CoinDesk.

The research that Flashbots details will allow blocks to be built without revealing data on users’ transactions, a step toward enhancing privacy.

Flashbots has not given an immediate timeline when it will move out of the testnet.

Block builders are specialized third-party participants who construct blocks based on optimizing transactions. Block builders offer those blocks to relays, such as the relay Flashbots runs for MEV-Boost, in order to extract extra revenue made from reordering or including certain transactions.

A mempool is like a waiting room, where pending transactions are sorted and stored before they are added to create a new block.

Flashbots told CoinDesk the move aims to enable privacy features on Ethereum. The code was made open source in an effort to decentralize block building on the Ethereum protocol.

“​​Implementing block building inside encrypted enclaves brings us one step closer toward transaction confidentiality and decentralization of the block building role,” Flashbots wrote in a blog post.

This is not the first time that Flashbots has made its code open source. In August, when Tornado Cash was sanctioned by the U.S. Treasury’s Office of Foreign Asset Control, Flashbots conveyed that its relay would also be censoring Tornado Cash transactions. As a result, Flashbots raced to open its code so others could decide whether to censor or not censor.

One reason open-source software is part of the Flashbots agenda is so others in the block-building space can “build off the shared knowledge and test other solutions,” the Flashbots team told CoinDesk. “And, in reality, try to break it!”


Please note that our privacy policy, terms of use, cookies, and do not sell my personal information has been updated.

The leader in news and information on cryptocurrency, digital assets and the future of money, CoinDesk is a media outlet that strives for the highest journalistic standards and abides by a strict set of editorial policies. CoinDesk is an independent operating subsidiary of Digital Currency Group, which invests in cryptocurrencies and blockchain startups. As part of their compensation, certain CoinDesk employees, including editorial employees, may receive exposure to DCG equity in the form of stock appreciation rights, which vest over a multi-year period. CoinDesk journalists are not allowed to purchase stock outright in DCG.

Margaux Nijkerk

Margaux Nijkerk reports on the Ethereum protocol and L2s. A graduate of Johns Hopkins and Emory universities, she has a masters in International Affairs & Economics. She holds a small amount of ETH and other altcoins.

Learn more about Consensus 2024, CoinDesk’s longest-running and most influential event that brings together all sides of crypto, blockchain and Web3. Head to consensus.coindesk.com to register and buy your pass now.