0x264A
August 1st, 2022

Scroll is an EVM-equivalent zkRollup to scale Ethereum. Technically speaking, Scroll is built upon two major pieces. The core piece is the zkEVM, which is used to prove the correctness of EVM execution in Layer 2. We have been building it in the open with the Privacy and Scaling Explorations group at the Ethereum Foundation for over a year. But to turn the zkEVM into a full zkRollup on the Ethereum, we also need to build a complete L2 architecture around it.

In this post, we give an overview of Scroll’s overall architecture. More specifically, we will cover the initial version of Scroll which is composed of a centralized sequencing node and decentralized proving network. We are committed to decentralizing the set of sequencing nodes in the future and will share our design for this in future articles.

Scroll's architecture

The current architecture consists of three infrastructure components (see Figure 1):

0x264A
July 21st, 2022

To scale Ethereum with our zkEVM-based zkRollup, we have designed Scroll based on a set of technical principles which uphold Scroll's core values. This post lays out these principles and how they relate to our broader design for Scroll.

Our technical principles

1. Ensuring user security

In the context of blockchain scaling solutions, the most important form of security concerns the integrity of user funds and data. Although a scaling solution may offer users additional capabilities, we believe ensuring users maintain access to their funds comes first. For Scroll, this means users should not need to rely on the honesty of Layer 2 nodes for security and can instead take advantage of full Layer 1 security even when transacting on Layer 2. By building on Ethereum according to this principle, we are rooting the security of Scroll in the most secure and decentralized consensus of the Ethereum base layer.

0x264A
July 19th, 2022

After over a year of building our zkEVM-based zkRollup in close collaboration with the PSE (Privacy and Scaling Explorations) group at the Ethereum Foundation, we are releasing the pre-alpha version of Scroll for external testers! In the spirit of building in the open with the community, we have prioritized getting community feedback quickly with this initial release.

If you’d like to be an early tester, sign up at signup.scroll.io for access. We will invite as many testers as possible while we drive towards a permissionless, public release.

What’s in the pre-alpha testnet?

This initial release will be run on a private PoA fork of Ethereum (the testnet L1) operated by Scroll. On top of this private chain, we will run a testnet Scroll L2 supporting the following features:

0x264A
June 13th, 2022

The promise of Ethereum is to build a decentralized computing platform widely accessible to all. Though it has come a long way towards achieving this vision, untenably high gas fees and frequent congestion on the current network present a significant challenge for true accessibility. Of course, the Ethereum community is aware of these issues and has adopted a rollup-centric roadmap to increase throughput. This roadmap focuses Ethereum on being the most decentralized settlement layer and moves execution to rollups on Layer 2.

We have long believed that rollups are the only viable way today to scale blockchains without sacrificing decentralization and security. However, until recently, technical obstacles meant that they were impractical to scale, driving users to alternative Layer 1s and sidechains, where scalability comes at a cost. Early last year, as researchers working in this field, we realized recent breakthroughs in ZK proof systems and hardware acceleration meant it was finally practical to build a general purpose EVM-equivalent ZK-rollup. Using the magic of ZKPs, this removes the tradeoff between security and scalability, offering the best solution for blockchain users and developers -- minimal trust assumptions, fast finality, and seamless migration from the base layer.

While coming to these ideas, we were inspired by the community-centric, open and collaborative values of the Ethereum community. In addition to technical considerations, we believe this cultural and social bonding creates a robust foundation for a global settlement layer and is hardly matched by any other crypto community.

With this in mind, we set out to build Scroll -- an EVM-equivalent ZK-rollup in early 2021 as part of the vibrant Ethereum ecosystem. Scroll uses zkEVM as its core component to prove the native EVM execution trace and leverages a decentralized proving network to solve the efficiency problem on the prover side. As we move closer to a public release one year in, this post lays out our vision and the values that inspired this effort.