Timelock Shield: A Robust Defense Against MEV and Censorship Attacks in Blockchain
Saksham Agrawal, Vinay J. Ribeiro · 2025
Blockchain’s security relies on cryptographic principles to resist tampering and fraud. However, vulnerabilities such as Maximum Extractable Value (MEV) and Censorship attacks persist, where malicious actors exploit knowledge of pending transactions or bribe miners to manipulate execution. While some state-of-the-art methods aim to counter these attacks through trusted setups and fair ordering, they compromise decentralization. Alternative solutions based on commit-and-reveal are decentralized but vulnerable to DoS and deferred reveal attacks. We introduce Timelock Shield, a decentralized protocol to counteract MEV and censorship attacks. Timelock Shield utilizes timelock encryption and delayed transaction execution related to a particular smart contract. Timelock encryption ensures that the transaction contents remain confidential until a cryptographic puzzle is resolved, and delayed execution allows the state of the smart contract related to that transaction to be updated later. Crucially, the protocol operates without requiring a trusted setup, directly addressing the vulnerabilities of existing methods and significantly enhancing both security and applicability. We present a detailed game-theoretic analysis of the complex incentive structure of the protocol for various participants, demonstrating the ineffectiveness of censorship attempts and the impracticality of MEV strategies. Furthermore, we detail the implementation of Timelock Shield’s key features based on Wesolowski’s Verifiable Delay Function (VDF), which enables the generation of encrypted transactions, decryption, proof generation, and transaction verification. Drawing from our experimental analysis, we offer insight into the selection of VDF parameters and deadlines used in the protocol to better align with real-world computational durations.