# Towards a Formal Foundation for Blockchain Rollups

**Authors:** Stefanos Chaliasos, Denis Firsov, Benjamin Livshits  
**arXiv:** [2406.16219](https://arxiv.org/abs/2406.16219)  
**Date:** 2024-06-23  
**Summary page:** https://www.summarizepaper.com/en/paper/2406.16219v1/

## Key points

- Blockchains like Bitcoin and Ethereum have revolutionized digital transactions.
- Scalability issues are a challenge for blockchain networks.
- Layer 2 solutions, such as ZK-Rollups, have been introduced to process transactions off-chain and improve scalability.
- Concerns about security and censorship resistance arise due to centralized control in Layer 2 solutions.
- The study uses the Alloy specification language to analyze and design key functionalities of Layer 2 mechanisms, including forced transaction queues, safe blacklisting, and upgradeability.
- Identifying vulnerabilities in current models and proposing enhanced designs aims to enhance security standards for rollups.
- Complexity and solving time increase with more intricate models, highlighting the critical need for secure implementation of Layer 2 mechanisms.
- Alloy models can guide low-level protocol implementation and generate tests to validate Solidity contracts against potential vulnerabilities.
- Integrating security properties into platforms like L2Beat provides accurate information about rollup risks to users.
- Collaboration with Matter Labs aims to design secure mechanisms for zkSync Era rollup contracts.

## Summary

Blockchains like Bitcoin and Ethereum have revolutionized digital transactions. However, scalability issues continue to be a challenge. To address this problem, Layer 2 solutions such as ZK-Rollups have been introduced to process transactions off-chain and improve scalability. While these solutions offer promising results, concerns about security and censorship resistance arise due to centralized control in Layer 2. This study utilizes the Alloy specification language to analyze and design key functionalities of Layer 2 mechanisms including forced transaction queues, safe blacklisting, and upgradeability. By identifying vulnerabilities in current models and proposing enhanced designs, the research aims to enhance security standards for rollups. The analysis includes statistics on code lines, generated clauses, and solve time for different rollup mechanisms. It is evident that the complexity and solving time increase with more intricate models, highlighting the critical need for secure implementation of Layer 2 mechanisms. Furthermore, this study explores how Alloy models can guide low-level protocol implementation and generate tests to validate Solidity contracts against potential vulnerabilities. The research emphasizes the importance of integrating security properties into platforms like L2Beat to provide accurate information about rollup risks to users. Collaboration with Matter Labs aims to design secure mechanisms for zkSync Era rollup contracts. Additionally, the paper discusses related work on formal methods for web security by drawing parallels between analyzing web platform security using Alloy models and evaluating rollup designs under threat models. In conclusion, this study provides a framework for designing and evaluating Layer 2 mechanisms with a focus on security and censorship resistance. By quantifying new lines of code written, clauses generated, and solve time using an SAT solver, the research demonstrates the increasing complexity of rollup mechanisms. The exponential growth in solving time with scope expansion underscores the need for robust security measures in Layer 2 implementations.