Sequencer Level Security

TL;DR

The paper introduces the Sequencer Level Security (SLS) protocol for rollups, enabling detection and quarantine of malicious transactions to enhance security without compromising decentralization.

Contribution

It proposes a novel security protocol for rollup sequencers to identify and isolate malicious transactions, improving trustworthiness of blockchain scaling solutions.

Findings

Prototype implementation called Zircuit on Geth and OP stack.

SLS protocol can be generalized to other rollup designs.

Enhances security by quarantining malicious transactions.

Abstract

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.