F3B: A Low-Overhead Blockchain Architecture with Per-Transaction Front-Running Protection

TL;DR

F3B introduces a blockchain architecture that uses threshold cryptography to protect transaction privacy until finalization, effectively preventing front-running attacks while maintaining low latency and compatibility with existing systems.

Contribution

F3B is the first blockchain architecture to provide per-transaction front-running protection using threshold cryptography, ensuring privacy even with delays and without altering consensus mechanisms.

Findings

Negligible 0.026% increase in transaction latency on Ethereum

Effective prevention of front-running attacks through delayed key revelation

Compatible with existing smart contracts and consensus algorithms

Abstract

Front-running attacks, which benefit from advanced knowledge of pending transactions, have proliferated in the blockchain space since the emergence of decentralized finance. Front-running causes devastating losses to honest participants and continues to endanger the fairness of the ecosystem. We present Flash Freezing Flash Boys (F3B), a blockchain architecture that addresses front-running attacks by using threshold cryptography. In F3B, a user generates a symmetric key to encrypt their transaction, and once the underlying consensus layer has finalized the transaction, a decentralized secret-management committee reveals this key. F3B mitigates front-running attacks because, before the consensus group finalizes it, an adversary can no longer read the content of a transaction, thus preventing the adversary from benefiting from advanced knowledge of pending transactions. Unlike other mitigation systems, F3B properly ensures that all unfinalized transactions, even with significant delays, remain private by adopting per-transaction protection. Furthermore, F3B addresses front-running at the execution layer; thus, our solution is agnostic to the underlying consensus algorithm and compatible with existing smart contracts. We evaluated F3B on Ethereum with a modified execution layer and found only a negligible (0.026%) increase in transaction latency, specifically due to running threshold decryption with a 128-member secret-management committee after a transaction is finalized; this indicates that F3B is both practical and low-cost.