Ethereum is considering encrypting its public mempool to shield pending trades from predatory bots, aiming to curb sandwich attacks while preserving open access for users and builders.
Ethereum developers are exploring a major change to how pending transactions are handled, aiming to protect users from trading bots that exploit the network's public mempool. The mempool, a transparent queue where transactions wait before being added to the blockchain, has long allowed automated bots to scan for profitable trades and insert their own transactions to extract value at users' expense. This practice, known as a sandwich attack, involves a bot spotting a pending swap, buying the same asset to move the price, and then selling after the user's trade executes at a worse rate.
Encryption Proposals
To address this, protocol researchers are preparing to discuss encrypting the mempool so that transaction details remain hidden until their order in a block is finalized. The leading proposal, EIP-8184 or LUCID, would require block builders to commit to sealed transactions containing an encrypted payload and a chargeable ticket, without knowing the transaction's contents. Only after the block order is set would the sender or a designated key publisher reveal the decryption key. This approach is designed to prevent both bots and block builders from exploiting transaction information before it is finalized, while still allowing anyone to submit transactions without permission.
Trade-Offs and Technical Hurdles
While encrypting the mempool could reduce front-running and sandwich attacks, it introduces new technical and operational challenges. LUCID's authors note that a fully secure scheme at Ethereum's scale would require small public keys, non-interactive decryption, no trusted setup, practical ciphertext sizes, strong chosen-ciphertext security, and a credible path to quantum resistance. No existing cryptographic construction currently meets all these requirements for Ethereum's throughput and user base. As a result, the current draft leaves decryption key management outside the core protocol, allowing senders to choose how and when to release keys, or to rely on third-party publishers. This flexibility could support stronger cryptography in the future, but also means users must trust their chosen key publisher to act reliably and on time.
Enforcement and Security Risks
One of the most difficult issues is how to enforce penalties if a key publisher withholds or prematurely sells a decryption key. The protocol can whitelist authorized publishers, but cannot always distinguish between deliberate misconduct, software failure, or network delays. If a key is not revealed as scheduled, the current LUCID draft places the penalty on the transaction sender, not the publisher. Other approaches, such as threshold decryption or trusted hardware, introduce their own risks and dependencies. Any production deployment would also need to coordinate with Ethereum's broader roadmap, including the FOCIL (EIP-7805) inclusion-list pipeline, which is targeted for the Hegotá upgrade in 2027.
Market Impact and Next Steps
Sandwich attacks have declined from their peak but remain a persistent risk for Ethereum users. In April, even Ethereum co-founder Vitalik Buterin was targeted by the Jaredfromsubway.eth bot, which front-ran and back-ran a small swap from one of his addresses. While some traders already use private relays to bypass the public mempool, this comes at the cost of relying on intermediaries who control transaction inclusion. An encrypted public mempool could offer a middle ground, preserving open access while reducing information leakage. The upcoming "Encrypt the Mempool" call on August 19 will bring together protocol researchers to debate whether a temporary, non-quantum-safe solution is acceptable and how to address enforcement challenges. For context, recent reporting by EgonCoin has highlighted how Ethereum's push for quantum-resistant upgrades is already forcing institutions to rethink their infrastructure timelines, as seen in analysis of the network's quantum-safe migration plans.
According to data from EigenPhi, sandwich attacks on Ethereum peaked in 2022, with daily losses sometimes exceeding $1 million. By mid-2024, average daily losses had dropped below $200,000, reflecting both improved user awareness and the adoption of private transaction relays. However, the risk remains significant for high-value trades and less experienced users, especially during periods of network congestion or volatile market conditions.
Encrypting the mempool would fundamentally change how transaction ordering and visibility work on Ethereum. While it could reduce the risk of predatory trading strategies, it would also introduce new dependencies on cryptographic schemes, key management, and enforcement mechanisms. Users would need to weigh the benefits of greater privacy against the risks of key publisher failure or collusion. As Ethereum's roadmap evolves, the debate over mempool encryption will test the network's ability to balance permissionless access, security, and practical usability for a global user base.
