Current blockchains do not provide any security guarantees to the smart contracts and their users as far as the content of the transactions is concerned. In the spirit of decentralization and censorship resistance, they follow the paradigm of including valid transactions in blocks without any further scrutiny. Rollups are a special kind of blockchains whose primary purpose is to scale the transaction throughput. Many of the existing rollups operate through a centrally operated sequencing protocol. In this paper, we introduce the Sequencer Level Security (SLS) protocol, an enhancement to sequencing protocols of rollups. This pioneering contribution explores the concept of the sequencer's capability to identify and temporarily quarantine malicious transactions instead of including them in blocks immediately. We describe the mechanics of the protocol for both the transactions submitted to the rollup mempool, as well as transactions originating from Layer one. We comment on topics such as trust and decentralization, and consider the security impact on the protocol itself. We implement a prototype of the SLS protocol, Zircuit, which is built on top of Geth and the OP stack. The SLS protocol described can be easily generalized to other rollup designs, and can be used for purposes other than security.

翻译：当前区块链在交易内容方面，并未为智能合约及其用户提供任何安全保障。秉承去中心化和抗审查的精神，它们遵循将有效交易直接纳入区块而不进行进一步审查的范式。Rollup是一种特殊的区块链，其主要目的是提升交易吞吐量。许多现有Rollup通过中心化运作的排序协议运行。本文提出排序器层级安全（Sequencer Level Security, SLS）协议，这是对Rollup排序协议的增强。这一开创性贡献探索了排序器识别并临时隔离恶意交易而非立即将其纳入区块的能力。我们描述了该协议对提交至Rollup内存池的交易以及源自Layer 1的交易的处理机制，并就信任、去中心化等议题进行讨论，同时考量其对协议本身的安全影响。我们实现了SLS协议的原型——Zircuit，该原型基于Geth和OP Stack构建。本文描述的SLS协议可轻松推广至其他Rollup设计，并可应用于除安全性以外的其他目的。