Rollups Optimistic
Transaction data is transmitted down and kept on Ethereum's mainnet while transactions are being executed on the rollup outside of Ethereum. Gas rates on optimistic rollups are often substantially cheaper than on Ethereum mainnet because this strategy enables gas expenses on Ethereum to be spread over all of the transactions contained in the bundled rollup.
Optimistic rollups take the position that all off-chain-calculated transactions are correct and legitimate when they are posted to Ethereum without providing a proof of validity, thus the name. In order to counteract fraudulent transactions, a challenge period is implemented during which anybody can contest the transactions that have been uploaded. The optimistic rollup will re-execute the legitimate transactions and update their state if it is determined that fraudulent transactions have been included. If, on the other hand, no valid challenge is made during the challenge period, the transaction is considered completed.
ZK-Rollups
Zk-rollups, on the other hand, are far more pessimistic. Zk-rollups do off-chain calculations as well, but they also give a cryptographic proof to show that the state update they are sending to Ethereum is the genuine result of all the transactions that have taken place on the zk-rollup.
The term "zero-knowledge" refers to these validity proofs, which enable any participant to independently confirm the veracity of the state update without being aware of the specifics of the transactions that preceded it. There is no need for a challenge period on zk-rollups because they can prove the veracity of their transactions. In contrast to optimistic rollups, zk-rollups only need to broadcast the proofs of each transaction, not the entire transaction.
Nevertheless, this comes with the added responsibility of producing the fraud proof, which may be time-consuming, resource-intensive, and frequently calls for a high degree of skill.
ZkSNARKs vs. ZkSTARKs: Differences and Similarities
Both zkSTARKs and zkSNARKs (Zero-Knowledge Scalable Transparent Argument of Knowledge) aim to allow zk-proofs and blockchain scalability. Yet, there are some notable distinctions between them.
The privacy protocol ZCash was essential in making ZkSNARKs more well-known. ZkSNARKs also have a lot lower proof size, which means that they take significantly less time and gas to verify. Nevertheless, this resulted in a significantly longer time required to compute the proof.
But, zkSTARKs also have their own advantages. This also implies that the chain may be vulnerable to future vulnerabilities from malevolent actors if the setup procedure was not carried out properly. ZkSTARKs are immune to this type of assault since they do not employ trusted setup. Moreover, zkSTARKs often provide proofs more fast, allowing them to possibly scale more effectively.
In early 2023, optimistic rollups like Arbitrum and Optimism gain the lead, but zk-rollups are gradually catching up. The market is particularly enthusiastic about zk-rollups that are compatible with the Ethereum Virtual Machine (EVM).
What Are ZkEVMs?
ZkEVMs are zk-rollups that are completely compatible with the EVM, as described above. This implies that any application now running on Ethereum or any EVM-compatible chain, such Polygon and Avalanche, may be ported to a zkEVM with little to no changes to the original code.
After all, the bulk of Total Value Locked (TVL) has always been on Ethereum, with the chain holding more than 50% of all TVL at any one time. As a result, it should come as no surprise that Ethereum developers have shown interest in competing Layer-1 (L1) chains that are EVM compatible.
Similar to this, zk-rollups like StarkNet, which are already operational on the mainnet, have not seen much adoption since they are not compatible with the Ethereum Virtual Machine (EVM) and there are no large decentralized applications (Dapps) on the chain. Many crypto users are eager to investigate their alternatives in the zkEVM market as a result of the surge of announcements from key zkEVM businesses in the industry in early 2023.
ZkEVM polygon
In contrast to rollups, which might take over the security of the parent L1, sidechains are in charge of their own security. Yet, the Polygon sidechain was still quite profitable. In addition to being a prominent participant in the DeFi summer of 2020, it recently scored big commercial development successes by partnering with companies like Starbucks, Adidas and Prada, Reddit, Stripe, and others.
Under the scenes, Polygon did considerable scaling effort, purchasing zk-rollup Hermez and zk-focused project Mir.
Nevertheless, Polygon's zkEVM has attracted the greatest buzz because to its impending March 27, 2023 mainnet debut.
Polygon says that its current proving system is the quickest in the world as a result of this combination of Polygon Zero's technology.
In addition, Polygon zkEVM makes use of recursive STARKs, which, in layman's terms, implies that whereas typical zk-rollups combine several transactions into a single proof for upload, recursion allows multiple proofs to be combined into a single large proof. This enables cost reductions and lowers latency, allowing Polygon's zkEVM to grow even more effectively.
ZkEVM from ConsenSys
ConsenSys, which was founded in 2014 by Ethereum co-founder Joseph Lubin, is responsible for some of the most popular crypto products, such as the hot wallet MetaMask and the infrastructure protocol Infura.
ConsenSys released a private beta of their zkEVM testnet in late 2022, and will release a public beta on March 28, 2023.
They are based on zkSNARK technology, but they employ a novel, in-house developed, lattice-powered prover to get around some of the technology's key drawbacks.
Their prover, which they have been working on since 2021, enables the fast generation of zkSNARK proofs. Even more crucially, it is demonstrated in a study article by ConsenSys researchers that ConsenSys zkEVM will not even need a trusted setup. Since it needs the user to intrinsically trust that the setup was done correctly, the trusted setup has long been considered zkSNARKs' weakest link. The tide and public view of zkSNARKs may be turned, nevertheless, by ConsenSys' significant advancement.
Scroll
Scroll, one of the lesser-known companies in the sector, is not unfamiliar with zkEVM technology. Scroll debuted on the Goerli testnet on February 28, 2023, following 1.6 million transactions on their pre-alpha testnet.
Scroll, like ConsenSys, has recognized the zkSNARK design's original shortcomings and implemented fixes. Scroll employs a modified version of ZCash's "Halo2" code, which enables protocols to take advantage of zkSNARKs' tiny proof size and speedy proof verification without requiring a rust setup.
Scroll's architecture, which is written in Solidity without the need of intermediate compilers to translate between different programming languages, reflects their desire to be as true to the EVM as possible.
In reality, the Scroll team contributes to the community-built zkEVM layer, which was developed in collaboration with the Ethereum Foundation's Privacy and Scaling Explorations (PSE) team and other groups working on zkEVM-related projects. Equivalence with Ethereum is a step above that with the Ethereum Virtual Machine (EVM), meaning that any application written for Ethereum will execute without modification or the use of intermediary layers.
In addition, following the launch of Scroll's mainnet, decentralization of the prover network and the sequencer in their roadmap is already planned in accordance with the Ethereum philosophy of decentralization.
ZkSync Era
As a project to help Ethereum grow via zk-proofs, ZkSync was developed by the blockchain engineering and research team Matter Labs. Their initial entry into the zk- rollup market was zkSync 1.0, which has since been renamed as zkSync Lite. Nevertheless, smart contract support was not available when zkSync 1.0 was released. Thankfully, issue was addressed in zkSync 2.0, which included smart contract support via the Zinc language. zkSync 2.0 announced in February 2023 that it will change its name to zkSync Era and add new capabilities to the rollup.
ZkSync Era supports Account Abstraction in addition to smart contracts. Account Abstraction, which just gained support on the Ethereum mainnet with ERC-4337, enables, among other advantages, more adaptable authentication logic, gasless transactions, and improved wallet recovery for users.
PLONK, a system based on zkSNARKs, is used by zkSync Era for its proofs in the backend. PLONK enhances zkSNARKs' work by making the trusted setup ubiquitous and upgradeable. While updatable implies that any user can keep adding randomness throughout the setup until they are satisfied that the setup is not compromised, universal indicates that the setup only has to be done once and can be reused by all circuits. It makes it simple to incorporate a huge number of people in the arrangement, making it practically highly secure, even though it is not a perfect solution.
As of today, zkSync 2.0 is now known as the zkSync Era, and registered projects can now deploy on the platform on the mainnet before the platform officially opens to end customers in the second quarter of 2023. DeFi giants including Uniswap, Balancer 1inch, LayerZero, and others have signed up to deploy, numbering more than 150 projects. Dapps written in other languages may be deployed on zkSync Era with relative simplicity and few code adjustments thanks to ZkSync Era's compiler, which also supports Solidity, Vyper, and Rust.
Taiko
Taiko, which was established in 2022, is the youngest company on the list. Its founders worked on Loopring, the first zk-rollup to be implemented on Ethereum, therefore their team is not brand new to the field.
Taiko aspires to be a Type 1 zkEVM, which means it will be completely Ethereum-equivalent rather than merely an EVM.
Taiko uses zkSNARK proofs for their rollup as their proving model. Taiko's protocol was created to avoid the need to wait for a proof if the transaction occurs on the rollup, only requiring it for cross-layer transactions like bridging, in recognition of the time needed to develop proofs for zkSNARKs. The time needed for proof creation, which is a key drawback of zkSNARKs, can be significantly reduced as a result. In addition, Taiko is looking on various bridge approaches that do not need the generation of full zk-proofs.
Conclusion
The race to grow Ethereum has never been more intense, with multiple zkEVM solutions launching their separate mainnets in 2023. Not to add, the majority of these solutions have the possibility for an airdrop.
Players like StarkNet, who do not yet support EVM natively, are also investigating transpilers to bridge the gap in programming languages. As they compete for dominance in the zk- rollup area and against their hopeful competitors, the rest of 2023 will undoubtedly be an exciting period for zkEVMs.
Neither the author nor the reader should take anything in this post as financial advice.
