What is Scroll?

About Scroll

Scroll was established in 2021 and is a zk-Rollup Ethereum scaling project that is EVM-compatible. It aims to create a universal network that provides developers with the same user experience and security as Ethereum, but with higher throughput, faster verification, and cheaper gas fees than Ethereum.

The project opened its pre-alpha testnet in August 2022, followed by the Alpha testnet on Goerli in February 2023. The mainnet is scheduled to launch in October 2023, and many ecosystems and contracts are expected to be deployed on Scroll. The project has already raised $80 million in funding, with Polychain Capital leading the investment and other well-known institutions such as Sequoia China, IOSG, and Qiming Venture Partners also participating. The valuation of Scroll has reached $1.8 billion.

Scroll’s founding team

Zhang Ye, who graduated from Peking University, has been engaged in research on zero-knowledge proofs since 2018. He is mainly responsible for the technical research of zk-Rollup in the Scroll team.

Sandy Peng, graduated from the University of Cambridge, and previously worked at the Hong Kong Securities and Futures Commission. In the Scroll team, she is mainly responsible for business, financing, and operations.

Shen Haichen, who graduated from Tsinghua University, previously worked at Amazon to build robot learning systems. In the Scroll team, he is mainly responsible for engineering development.

How Scroll Works

The architecture of Scroll mainly consists of three components: Scroll nodes, proof network, and Rollup and cross-chain bridge contracts.

Scroll nodes can be understood as constructing a user’s Layer 2 network block from their transactions, then submitting it to the Ethereum mainnet and transmitting information between the mainnet and Layer 2 network. Scroll nodes consist of a sequencer, coordinator, and relayer.

Scroll Node Architecture (Source: https://scroll.io/blog/architecture)

The proof network is called Rollers, which serves as the prover for the network and is specifically responsible for generating validity proofs for the zk-Rollup network. Additionally, Rollers can utilize hardware devices such as GPUs and ASICs to shorten the verification time and cost.

Roll Network Validity Proof Path (Source: https://scroll.io/blog/architecture)

The verification bridge includes the Rollup contract and cross-chain bridge contract.

The Rollup contract mainly ensures the availability of Layer 2 network data and verifies zkEVM proofs. The cross-chain bridge contract allows users to transfer assets and information between Layer 1 and Layer 2 networks.

By combining these three components, the main operation flow of Scroll zk-Rollup is established. In simple terms, the sequencer creates a block sequence and generates its proof, which is then aggregated into a single proof and sent to the Rollup contract through the coordinator, where the blocks are validated and finalized.

Scroll zk-Rollup Operation Flow (Source: https://scroll.io/blog/architecture)

According to the flowchart, it can be divided into the following four steps:

1. The sequencer creates a series of sequences. For each block, the sequencer generates an execution trace T and sends it to the coordinator. At the same time, the transaction data D is submitted to the Rollup contract on Ethereum.
2. The coordinator randomly selects a Roller to generate a validity proof for each tracked block. To improve proof generation, different Rollers can generate proofs for different blocks.
3. The Roller sends the block proofs back to the coordinator. Every k blocks, the coordinator assigns an aggregation task to another Roller to aggregate the k block proofs into one proof A.
4. Finally, the coordinator sends the aggregated proof A to the Rollup contract, where the block is finalized based on the aggregated proof, the previously submitted state root, and transaction data commitment.

Scroll blocks are ultimately finalized on the Layer 1 network through these steps. Each Layer 2 network block goes through the following three stages until it is finalized:

1. Precommitted: Indicates that the sequencer has proposed a block and sent it to the Roller. Although precommitted blocks are not yet part of the specification of the Scroll Layer 2 chain because they have not been published on the Ethereum base layer, users who trust the sequencer can choose to take action on these blocks.
2. Committed: Indicates that the transaction data of the block has been published to the Ethereum network via the Rollup contract. This ensures the availability of block data but does not prove that it has been executed correctly.
3. Finalized: Indicates that the correct execution of the transactions in the block has been verified by being chained on Ethereum. Finalized blocks are considered part of the specification of the Scroll Layer 2 chain.

In summary, Scroll is able to execute native EVM bytecode on Layer 2 networks while maintaining the strong security guarantees of the underlying Ethereum layer.

Top zk-Rollup Projects Comparison

The competition in the ZK-Rollup track is fierce, with leading networks such as zkSync, Polygon, and Startnet actively expanding their ecosystems. In order for a new mainnet to compete in the ZK-Rollup track, it must have unique advantages.

Scroll

Scroll has two advantages. Firstly, it achieves zkEVM compatibility by focusing on bytecode compatibility. This means that applications on Ethereum can migrate to Layer 2 networks with minimal code modifications. Scroll provides a user and developer experience that is almost identical to Ethereum. Given the technical difficulty of zk technology, we can see that the ecosystem development on mature networks like zkSync and Startnet is still relatively slow. If Scroll can have stronger compatibility, it can attract ecosystem projects and tools from the Ethereum network more easily, greatly reducing the difficulty of developing Layer 2 networks.

The second advantage is Scroll’s decentralized validation network. Scroll has established a decentralized validation network that distributes ZKP transaction proofs to everyone for computation, enabling validators, node operators, developers, and community users to participate in a decentralized manner. This enhances the security of the Scroll network and avoids the risks of centralization or single cross-chain bridges. It also attracts more people to participate in their ecosystem and incentivizes participants to obtain ZKP mining rewards.

zkSync

zkSync has a unique data compression technology and strong scalability. However, it requires the rebuilding of a virtual machine at the language level, which is only used for language-level compatibility with EVM. Developers can program Layer 2 networks using Solidity and Zinc languages, but it requires a certain degree of redevelopment.

On the other hand, Scroll is working on bytecode compatibility. Bytecode compatibility means that Solidity, Vyper, and Huff can be directly used without the need for re-auditing, and most existing tools can continue to be used. This makes it easier for developers to build new ecosystems on the Scroll network.

Polygon zkEVM

Polygon zkEVM utilizes zero-knowledge proof technology to improve network scalability and privacy, and transaction costs are much cheaper than the Ethereum network. With a large user base and ecosystem applications, Polygon zkEVM can directly use existing Ethereum development tools and has strong competitiveness.

In terms of EVM compatibility, Polygon zkEVM currently achieves high compatibility, while Scroll network’s EVM equivalence provides a smooth user experience almost identical to Ethereum, directly supporting every EVM bytecode.

Starknet

Starknet adopts zk-STARK technology, which does not require initial security settings, and already has star applications such as DYDX. However, Starknet’s ecosystem development is limited due to the use of its own constructed language, Cairo. The sequencing and validation of Startware are operated by its own officials, and block production, validation, and packaging are managed by the project team. The code is not open source, and decentralized mining nodes have not been fully established, making it impossible for the community to participate. Scroll’s development of GPU validation ensures that anyone can set up a proof node.

Scroll Ecosystem

Technology is just the starting point, without ecosystem support, it will greatly limit the development of the mainnet. Scroll is actively expanding its ecosystem projects. As a newly launched mainnet, Scroll has already built more than 100 projects, distributed across various types such as DEX, DeFi, NFT, GameFi, and domains. Due to the unique advantages of EVM equivalence, most mature DeFi projects have already completed deployment.

Official Cross-Chain Bridge - Scroll Bridge

The official cross-chain operation is relatively simple. Just enter the amount to be crossed and click “Deposit Funds” to execute the entire asset cross-chain process. However, currently the official cross-chain bridge only supports cross-chain from the Ethereum mainnet to the Scroll network. The current gas fee for each unit of transaction is high (around 30-40 Gwei). To reduce transaction costs, users can choose to temporarily use third-party bridging services for cross-chain operations.

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Scroll official cross-chain bridge (Source: https://[scroll](https://www.coinonpro.com/tag/scroll).io/bridge)

Zada Finance

As the first cross-aggregated order book DEX on Scroll, Zada Finance is a cross-rollup order book DEX based on Scroll. Zada Finance aims to bring users more combinations, lower costs, and faster transactions, supporting account abstract wallets, order aggregation, and more flexible interest rate options. The official Twitter (now X) post clearly states that there will be airdrop rewards for testnet users.

Zada Finance Homepage (Source: https://www.zadafinance.com/swap)

Papyrus Swap

As a native DEX platform on Scroll, Papyrus is an automated liquidity protocol. Anyone can exchange pool tokens by depositing an equivalent amount of each underlying token, becoming a liquidity provider (LP) for the pool.

Cog Finance

Cog Finance is an independent lending platform on Scroll, supporting users to lend their preferred assets and choose the collateral they want to accept, earning profits by lending assets with continuously changing interest rates.

CogFinance Homepage (Source: https://www.cog.finance/)

Scroll Name Service

Scroll Name Service is a decentralized naming service developed on the Scroll mainnet. Scroll NS aims to provide an online identity solution for web3, requiring one-time payment of ownership fees, fair launch and distribution, and next-generation domain utility.

Scroll Name Service official website (Source: https://scroll.name/)

Scroll Tokenomics

Scroll has not yet released its tokenomic model.

After the launch of Scroll Mainnet, it has received increasing attention. Although the token has not been released yet, the market still has high expectations for the airdrop of Scroll, which is valued at 1.8 billion. With more and more ecological projects joining the Scroll Mainnet, users have more ways to participate in interactions, such as skydrome, iZUMi Finance, SynFutures, Symbiosis, spacefi, etc. Furthermore, it is necessary to continuously keep track of the development of Scroll’s ecosystem and interact once or twice a week.

In addition to Scroll’s own token, users can also pay attention to the airdrop opportunities of project tokens within its ecosystem. Gate will also help everyone keep an eye on the development of Scroll’s ecosystem and will inform everyone as soon as opportunities arise.

Conclusion

The competition in the zk-Rollup track has intensified, and Scroll, as an emerging project, has successfully stood out. Currently, it still focuses on ecosystem deployment, actively organizes hackathons, and cooperates deeply with ecological projects to enrich the mainnet infrastructure and expand the ecosystem.

Once zk-Rollups technology is widely applied, the global crypto ecosystem will experience a qualitative improvement. As the most widely adopted Ethereum scaling technology, Rollup will naturally have an impact on the Layer 2 network based on Ethereum’s vast ecosystem. Due to Scroll’s advantages of EVM equivalence and comprehensive decentralization, its own value will also experience significant growth.