Ethereum scaling solutions based on zero knowledge (ZK) rollups have exploded in recent times, and the technology’s proponents argue it represents the blockchain’s future. Already, there are over a dozen projects exploring ZK rollups for a variety of applications.
The latest Layer 2 to enter the fray — Scroll — launched discretely on October 8. But how can the new technology stand out in an increasingly crowded field?
To date, more than a dozen Ethereum scaling solutions have been developed that deploy ZK rollups.
Some of these are application-specific. For instance, the dYdX crypto exchange built its own ZK roll-up system to help reduce fees for users.
Other solutions are more ambitious, like Loopring, which used the technology to build a general-purpose business platform for trading, swapping, liquidity provision, and payments.
Finally, at the most universal level, L2s like Starknet, ZKSync Era, and Linea are open to any Web3 application that could benefit from the scalability and lower gas fees offered by ZK rollups.
Although there are plenty of ZK rollup-based L2s already available, Scroll was developed with the vision of creating a user-friendly platform for the full spectrum of decentralized applications (dApps).
One major challenge Ethereum developers faced when working with ZK rollups was the lack of full compatibility with the Ethereum Virtual Machine (EVM). As such, they remain out of reach for many Ethereum dApp developers.
However, Scroll contributes to recent advances in EVM-compatible rollups known as zkEVMs.
In fact, the new platform could even be the first “type 1” zkEVM according to Vitalik Buterin’s four-part categorization whereby type 1 zkEVMs “strive to be fully and uncompromisingly Ethereum-equivalent.”
The lack of strong Ethereum equivalence in existing solutions makes them very difficult to use for the average dApp developer. Many ZK rollups require the use of obscure programming languages and a deep understanding of zero-knowledge proofs.
However, with Scroll, developers can implement smart contracts using any EVM-compatible language.
Arguing that existing solutions are “developer-unfriendly,” Scroll’s developers have said they want to “provide the best developer experience […] so that existing Ethereum applications can simply migrate over onto the zk-Rollup as is.”
The ZK in ZK rollups refers to the use of zero-knowledge proofs: a cryptographic process for verifying information without revealing its content.
ZK rollups offload complex computation and state storage off-chain, processing numerous transactions in a batch and posting only summarized data to the Ethereum mainnet. Using ZK proofs, they can succinctly verify that the summary data is true.
A major obstacle to the widespread use of ZK proofs is the time necessary to generate them. For example, the ZCash network can take over 30 seconds to generate proof for each anonymous transaction. Meanwhile, Filecoin requires around an hour to make each proof.
However, Scroll co-founder Ye Zhang has developed a new hardware acceleration method that can increase the speed of proof generation by 100x.
In a recent blog post , Zhang observed that the ultimate goal for the Ethereum community was to “build an Ethereum-equivalent zkEVM which can be used to prove mainnet blocks.”
He also proposed a future Ethereum in which “validators don’t need to re-execute a layer 1 block, but instead, they only verify a succinct zk proof.”
The dream is surely a lofty one, which could dramatically streamline Ethereum’s entire operation. “Imagine one day, you can prove the whole history of Ethereum via one single proof,” Zhang said. “Isn’t that super exciting?”