The battle for zero knowledge EVM compatibility is currently raging and the once mythical EVM compatible zk-rollup has been achieved by 3: zkSync, Polygon, and Scroll. Scroll is the only one that is claiming to have an EVM-equivalent zk-rollup (after Polygon walked back their claims of EVM Equivalence and stated that they are EVM Compatible). What is the difference between EVM equivalence and compatibility? What else does Scroll bring to the table in the battle for zero knowledge layer 2 dominance? Lets dive in to the protocol that has raised over $30 Million in Series A Funding.
Equivalence vs Compatibility
EVM compatibility means that the L1 contracts for the L2 solution responsible for committing the bundle of rolled up transactions, verifying their integrity, and processing fraud proofs does not implement the EVM itself. Instead, it implements a compatible subset small enough to be able to identify inconsistent state changes inside of the transactions within the Rollup, when fraud proofs are submitted (i.e. able to execute the state change of a transaction as if it was the actual EVM).
EVM compatibility reduces the amount of gas required for the fraud-proof verifier contract and its execution (not having to implement the full EVM means less code), and is good enough for the EVM code used by almost every application, but not for every application.
EVM equivalence, on the other hand, means that the L2 protocol is completely compliant with Ethereum and the EVM. With this, any code that can be run in L1 can also be run in its L2 counterpart with the exact same functionality as the L1. This integrates the full Ethereum stack in the L2 system, so that every Ethereum contract, every toolchain, and even every node implementation compatible with L1 is also compatible with L2. In the simplest of terms, it is “copy + pasteable” without any edits needed. The benefits of this are tremendous as any application built on top of not only Ethereum, but every EVM equivalent Layer 1 and Layer 2 as well, can use any code across all of those networks, making it easy for applications that were initially built elsewhere to migrate to Scroll by simply (maybe not so simply) copy/pasting.
The Vision Behind Scroll
The team behind Scroll, like many others within the Ethereum ecosystem, believe that decentralized computing platforms will play a crucial role in the future, and that the community behind Ethereum, its decentralization, security, and rollup-centric roadmap, made it the perfect ecosystem for them to build. The team believes in building with four main ideals in mind:
Empowering humanity through blockchain
Scroll aims to empower humanity by scaling Ethereum so that it can be assessible for billions of users. This requires making it both scalable and cheap enough to be accessible for all as well as being secure and having an easy user experience.
Building in the open with community involvement
Scroll aims to be community-centric and fully open-source from day one, believing blockchain and rollup technology to be so important that it should be open to everyone to view, understand and audit. That is why they use public specs and repos, and are collaborating with the Ethereum Foundation Privacy and Scaling Explorations team to build their zkEVM.
Decentralization
The team behind Scroll states that their end-goal aim is to achieve the same levels of decentralization and censorship resistance as Ethereum, although they believe the best way to approach this is gradually.
By using Ethereum for both consensus and data availability, Scroll inherits the same level of decentralization. Even in the case of a protocol failure, the team is building forced exit mechanisms into the protocol so that users are able to withdraw their funds even in the worst of circumstances.
Censorship Resistance
Censorship resistance is more challenging to achieve for rollups, but Scroll has a two step process for trying to tackle the issue.
First, Scroll has designed a decentralized proving protocol which allows rollup proofs to be outsourced to a community of Rollers, a permissionless and decentralized network of provers who generate proofs for Scroll Layer 2 blocks.
Scroll is hoping to have a robust Roller ecosystem competing to improve prover performance with hardware acceleration, and more importantly, enable users to run the prover themselves and force their transactions to a rollup batch in case of any attempted censorship. More on this below.
Second, Scroll aims to achieve full decentralization by decentralizing the sequencer. By then, anyone will be able to run a sequencer so that transactions cannot be censored.
The How Behind Scroll’s Goals
Keeping those ideals in mind, the team behind Scroll has introduced the principles by which they aim to achieve those ideals.
Security and EVM-equivalence lead us to a zkEVM-based zkRollup solution
In building Scroll, as should be in any project where consumer funds are at question, security is their first priority. Transactions on Scroll are guaranteed by zero-knowledge proofs verified in a smart contract on the Ethereum base layer. This makes Scroll transactions as secure as transactions on the Ethereum base layer itself, so as long as you trust the security of Ethereum, theoretically you should have the same level of trust in Scroll.
It is the belief of the Scroll team and many within the space that achieving EVM-equivalence through a zkEVM is the holy grail for processing commercial scale transactional throughput. The Scroll zkEVM proves the correct execution of native EVM bytecode using succinct ZK proofs, providing guarantees on the state transition function of the EVM itself and allowing Scroll to support Ethereum native developer tooling.
Decentralization leads us to a decentralized prover network
As mentioned above, the Scroll team decided to build our Roller network, a permissionless and decentralized network of provers who generate proofs for Scroll Layer 2 blocks.
There are two major technical benefits of our decentralized prover network:
Scroll designed their proving infrastructure to be highly parallelizable, meaning that Scroll is able to scale proving compute power simply by adding more proving nodes.
This will incentivize the community to build better hardware solutions and run provers themselves instead of relying only on the Scroll team in a centralized way, which is only possible because of Scroll’s commitment to being completely open source.
To bootstrap in the initial phase of the network, the team is building GPU prover solutions internally which will in turn be open-source for public usage, but the hope is that in the long run, the community will improve the prover solutions in a decentralized manner and competition in this domain will lead to exponentially decreased latency and cost for proof generation.
Second and most importantly, Scroll plans to also decentralize the sequencer over time alongside our prover network, providing greater censorship resistance for the protocol.
As Scroll approaches a fully live mainnet, they will continue to focus on optimization and integrating the newest and best techniques, such as
Data blobs post-danksharding to improve Scroll efficiency.
How to co-optimize Scroll's zkEVM with new hardware-friendly ZK algorithms
How to expose new ZK primitives to Layer 2 application developers
Not financial, legal or tax advice. This newsletter is strictly educational and is not investment advice or a solicitation to buy or sell any assets or to make any financial decisions. All opinions expressed are solely those of the individual author. This newsletter is not legal advice and does not create an attorney-client relationship. This newsletter does not constitute tax advice. Talk to your independent attorney and/or accountant for any questions specific to you. Always do your own research and use caution when interacting with smart contracts or the blockchain.