There is no shortage of Optimistic rollups; just this year we have seen Base, Mantle, and more launch.
But there is a growing cohort of blockchain leveraging ZK rollup tech, from zkSync to Polygon zkEVM, and now Scroll…
Learn about Scroll’s origin, what dApps have deployed, and what to expect going forward.
Stay alert, stay informed ⬇
Background on Scroll
Scroll is a native zkEVM rollup solution designed to scale Ethereum.
As a zkEVM, Scroll aims to bring the benefits of ZK proofs to a Layer-2 EVM.
The rollup has 4 stated technical principles:
Ensuring user security: the most important form of security concerns the integrity of user funds and data.
Maintaining EVM-equivalence: an effective Ethereum scaling solution should give users and developers a seamless migration path from existing dApps and developer tooling.
Efficiency: transaction fees should be low and users should experience instant pre-confirmation on Layer-2 and reasonably fast finality on the base layer.
Decentralization across all layers of the community: This includes node operators, provers, and the community of developers and users. By building in the open with the community and charting a credible path to decentralizing both proving and sequencing, Scroll is committed to ensuring decentralization across all dimensions.
Scroll’s launch marks a significant milestone; the team feels excited and accomplished after two years of hard work.
Scroll's focus has always been on maximizing compatibility with Ethereum.
While EVM compatibility is one of the most compelling aspects of the chain, the idea seemed unrealistic to some people initially.
Scroll Co-Founder Sandy Peng shared that many thought Scroll was actually a joke due to it’s ambitious goals.
Prioritizing EVM Compatability while maintaining scalability could prove difficult
Importance of EVM Equivalence
Toghrul Maharramov, Senior researcher at Scroll, believes that reusing existing infrastructure and documentation makes sense for wider adoption.
Rebuilding everything from scratch requires educating users about a new language and paradigm.
Leveraging existing resources in Solidity makes development easier and attracts more developers. Solidity's 10 years of documentation, tutorials, and open-source code are valuable assets.
EVM equivalence allows for compatibility and reuse of widely adopted building blocks. Scroll aims to be an extension of Ethereum, not a separate entity.
Toghrul beleives that optimistic rollups are seen as a short-term solution, while ZK rollups are considered more long-term.
He believes that all optimistic rollups will eventually transition to ZK rollups.
Being maximally compatible with Ethereum is a key strategy for Scroll.
The goal is to build something that meets developers where they are already.
Reusing battle-tested protocols, established brands, and existing codebases adds value to the ecosystem.
The goal is to reuse as much code as possible from Ethereum.
Certain modifications and optimizations are made, but the surface area of the new code is smaller.
Scroll currently uses a modified version of Geth, but it can adopt other execution clients easily.
Compatibility with Ethereum's execution trace allows relying on battle-tested code.
Other zkEVMs mainly focus on functional equivalence without bytecode compatibility.
Achieving true bytecode equivalence requires more effort but allows leveraging existing innovation in parallel.
Toghrul says that 99% of apps will work without modification on Scroll; developers are encouraged to reuse their existing code.
Optimistic vs ZK Rollups
ZK rollups aim to improve scalability by removing bottlenecks related to Ethereum, such as data availability.
The precise number of transactions per second (TPS) that Scroll can support is difficult to determine, but it is estimated to be at least an order of magnitude higher than Ethereum's TPS.
State growth is a challenge inherited from Ethereum, but because Scroll doesn't need to optimize for low-end devices, it can achieve better performance.
Toghrul says that the primary reason for using ZK rollups is not privacy but rather their property of succinctness in modern proof systems.
Succinctness allows for cheaper verification compared to recomputing costly executions.
ZK rollups benefit from outsourcing computation to a few large nodes and achieve faster finality compared to optimistic rollups.
Faster finality is achieved as proofs can be quickly published and verified without waiting for challenge periods like in optimistic rollups.
With ZK rollups, users can transact and send messages without delays, improving overall user experience.
With ZK rollups, the maximum wait time for exiting from layer-2 to layer-1 is around 30 minutes.
With optimistic rollups, the wait time can be up to a week.
Faster throughput in rollups translates into tangible benefits for users when processing thousands of transactions per second.
Fees can be much cheaper for end users with ZK rollups compared to optimistic rollups.
Market making becomes more competitive between ZK rollup and layer-1, resulting in lower taxes.
Cross-chain messaging plays a role in withdrawal times. For example, voting on layer-2 and sending the result back as a message to layer-1 would require waiting for a week with optimistic rollups but only 10-30 minutes with ZK rollups.
What to do on Scroll & Why Scroll
The Scroll mainnet launch has already taken place, allowing infrastructure projects to come on board.
Users can now bridge funds to Scroll through the public Bridge UI.
Developers can start deploying their dApps on Scroll.
Specific applications that work uniquely with ZK rollups or take advantage of lower costs and faster speeds are expected to be deployed in the coming weeks and months.
Current top-5 Selection of dApps on Scroll
For apps with a multi-rollup strategy, deploying on Scroll could potentially remove friction and offer an easy self-deployment process.
The combination of lower costs, faster speeds, and unique features enables the development of innovative and useful applications on Scroll.
Other key projects and protocols building on Scroll include:
LayerZero: LayerZero needs no introduction; the infrastructure protocols has gained traction for it’s ability to build endpoints between different chains, facilitating cross-chain communication.
The Graph: The Graph provides subgraphs, which can be used by developers to access data for a given blockchain, a critical component for building a high-quality dApp.
Orbiter Finance: Orbiter is a cross-chain bridge that now allows users to bridge up to 5 ETH directly onto Scroll Mainnet from Ethereum and a host of L2s and alt L1s.
Stitching Layer-2s Together
There are two main challenges: handling communication between different layer-2s and improving UX.
From Scroll's perspective, their main goal is to ensure developers know where they are deploying their applications.
Optimizations can be made on the UX side, such as defining new address types that indicate which chain is being used. ZK technology offers efficiency improvements that will likely address these challenges within the next two years.
Currently, there is no standardized way to bridge assets between different layer-2 solutions.
Fragmentation and lack of standardization still exist, but conversations about standardizing certain aspects have begun.
Research is also being conducted on bridging layer-2 solutions directly without going through layer-1.
Storage proofs and ZK can be used to prove state storage and bridge to another layer-2 without waiting for messages to pass through layer-1.
The process of bridging may vary depending on the type of layer-2 solution being used (e.g., ZK rollup or optimistic rollup).
Standardization efforts are focused on simpler aspects initially, such as introducing a new transaction type specific to layer-2s. The goal is to make asset bridging more seamless and user-friendly in the future.
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