Zero-knowledge rollups (ZK rollups, ZK-rollups, ZKRs) are among the hottest trends in Web3. The role this concept plays in scaling Ethereum allowed it to gain mainstream adoption in 2022-2023.
In this text, GetBlock is going to cover the basics of ZK rollup primitive and portray the most popular projects that leverage it for DeFi designs.
Best ZK rollup projects in 2023: Highlights
ZK rollups are designed to process some transactional data outside of Ethereum mainnet to save its computational resources and make its operations more speedy and cost-efficient.
- Zero-knowledge rollups is the cryptographical technology of data aggregation and verification;
- With ZK rollups, Ethereum-based system partially processes data outside of network mainnet;
- ZK-based system compresses data, aggregates the information about thousands of transactions into a single one and verifies it on Ethereum as such;
- In order to preserve the integrity and confidentiality of the information, ZK rollups generate zero-knowledge proofs;
- With ZK rollups, dApps can use Ethereum for trivial fees and way faster than interacting with its mainnet;
- StarkNet, zkSync, Aztec are among the most successful implementation of ZK rollups technology;
- Numerous Web3 giants - Coinbase, Polygon Network and so on - released their zkEVM networks that work with Ethereum code, but process data via ZK rollups;
- Some mainstream dApps including Aave, Uniswap, dYdX and Curve have already deployed their versions on ZK-based systems.
As such, with all its limitations and challenges, ZK rollup technology is the most promising way to scale Ethereum in terms of transaction throughput and usage costs.
What is ZK rollup technology?
ZK rollups represent a class of second-layer Ethereum (ETH) scaling solutions. Not unlike other L2 instruments (State Channels, Optimistic Rollups), they partially process transaction data outside of the chain to reduce the amount of data that has to be posted to the blockchain.
Image via HackMD
Technically, ZK rollups bundle (or 'roll up') transactions into batches that are executed off-chain. ZK rollups interact with Ethereum mainnet through a smart contract: once the transactions are ‘rolled up’, the prover generates cryptographic proof and transfers data to Ethereum-based smart contract.
How can ZK rollups scale Ethereum?
Every ZK rollup system consists of three elements necessary for its secure and effective operations:
- Smart contract on Ethereum network. It is responsible for interacting between the scaling solution and Ethereum: every transaction that happens on ZK rollup should also be mirrored on the main network.
- Third-party prover. The prover generates cryptographic proofs to guarantee the validity and integrity of data that is processed through the ZK rollup system. No one should be able to somehow corrupt the data during the process of compression. Also, the entire procedure should be executed in a ‘zero-knowledge’ manner: no party should be able to know the information that is transferred to Ethereum.
- Verifiers ecosystem. Verifiers are a subclass of blockchain validators: they’re nodes responsible for confirming the status of the proofs and submitting them to Ethereum mainnet.
Simply put, ZK rollups compress thousands of transactions and process it on Ethereum at the speed and price of the only transaction. While doing so, ZK rollups try to protect data from being visible to third parties or somehow tampered.
Top 5 ZK rollup projects of 2023: Comparison
Typically, there are two main groups of projects in the ‘ZK rollups’ category. The first one represents the subclass of ‘ZK rollups’ itself: they are blockchains that use this technology to scale Ethereum.
The applications that leverage the first category just like they used Ethereum or Polygon previously represent the second category.
Here are some examples of ‘ZK rollups’- blockchains:
- Polygon zkEVM
Let’s summarize the basic knowledge about some ZK rollup projects of 2023.
|N||Name||Mainnet launch||TVL, $ million||Token||Tech|
|1||StarkNet||April 2023||46||STRK||zk-STARKs, UTXO-based|
|2||zkSync||March 2023||310||N/A||PLONK, account-based|
|3||Polygon zkEVM||March 2023 (Beta)||7||MATIC||zkEVM|
|4||Aztec||July 2022 (for Aztec Connect)||11||N/A||zk-SNARKs|
|5||Scroll||Q3, 2023 (expected)||N/A||N/A||zkEVM|
Now, let’s review some of the most trending implementations of ZK technology, its advantages, challenges and limitations.
Developed by Israeli-based Web3 builders StarkWare Labs, StarkNet was among the first viable ZK-based systems in the Ethereum segment.
StarkNet is a permissionless ZK rollup blockchain written in Cairo, an original programming language. In early 2018, StarkNet was introduced by Eli Ben-Sasson, inventor of Zero-Knowledge Scalable Transparent Argument of Knowledge (ZK-STARK), one of ZK protocols.
Image by StarkNet Ecosystem
In 2020, its first implementation - StarkEx - was launched to scale operations of selected Ethereum dApps: Rhino, Sorare, and so on.
StarkNet’s architecture includes three off-chain components: Sequencer, Prover and Full Node. Sequencer receives the transaction from users, Prover batches them and creates cryptographic validity proof while Full Nodes track the changes of system status.
Also, it has two on-chain components: Verifier and StarkNet Core. Verifier receives the cryptographic proofs while Core updates the system to ensure L1-L2 consistency.
Typically, ZK-STARK is considered to be way more secure and scalable compared to other scaling technologies like Optimistic Rollups. For instance, in the future, there will be more Provers in StarkNet.
Also, it is quantum-resistant by default and much easier to customize.
Some researchers criticized the design of the StarkNet smart contract that connects it to Ethereum and the limitations of Sequencer/Prover interactions.
Developed by Matter Labs, zkSync saw its first iteration (now dubbed zkSync Lite) launched in June 2020. In 2023, it is the key newsmaker in the ZK rollups segment.
ZK rollups solution zkSync reveals one more methodology to scale Ethereum. Now it consists of two separate blockchains, zkSync Lite (formerly zkSync 1.0) and zkSync Era (formerly zkSync 2.0).
Image by zkSync
zkSync 1.0 was the first commercially viable implementation of ZK tech that accomplished nine-digit TVL while zkSync Era is the first zkEVM blockchain, i.e. ZK-based L2 network that can run the same code with the applications written for ‘native’ Ethereum Virtual Machine (EVM); this feature is called ‘EVM equivalence’.
Since v1.0 release, zkSync has leveraged PLONK i.e. ‘Permutations over Lagrange-bases for Oecumenical Non-Interactive Arguments of Knowledge’. This development replaced application-specific trusted setup by a universal and updateable setup that significantly reduced the time and effort for dApps development.
zkSync 2.0, besides EVM equivalence, boasts eccentric infrastructure where a ‘regular’ set of Full Node, Prover, and Interactor are accompanied by Paranoid Monitor that alerts Matter Labs about the incidents.
zkSync is the first ZK rollup project to add potential support for sharding via its zkPorter protocol. It also supports various smart contracts languages besides Zinc, which is its internal one.
Also, zkSync charges users with almost negligible fees. As displayed by L2Fees Info, its offering is the second cheapest as of Q2, 2023.
In March, 2023, some users reported slow L2-to-L1 withdrawals on the zkSync 2.0 network.
Polygon zkEVM is the first zkEVM solution developed by the blue-chip blockchain ecosystem, Polygon Network (MATIC).
Polygon zkEVM: Description
Launched in March, 2023, Polygon zkEVM leverages 100% EVM-equivalence with security and resource-efficiency of ZK proofs.
SEE ALSO: https://getblock.io/blog/polygon-matic-launches-a-news-gen-ls-scaling-solution-ethereum/
It allows Ethereum- and Polygon-based dApps to migrate to the L2 blockchain without altering their codebases.
Polygon zkEVM: Features
Polygon zkEVM pioneered applied usage of recursive STARKs. It resulted in 100x improvements in the most expensive operations in the zkEVM: Keccak, ECDSA, and Recursion.
Its Prover element is the most powerful in L2s segment: it is able to validate 500K gas units on a mediocre CPU server (64 cores) in just 300 seconds.
Polygon zkEVM: Advantages
Full equivalence with EVM (and, therefore, with all EVM ecosystem blockchains) makes Polygon zkEVM a go-to solution for dApps interested in leaving L1s. Also, it is backed by the great ‘ecosystem effect’ of Polygon, the largest EVM-compatible blockchain.
Polygon zkEVM: Disadvantages
Some users criticize the role of MATIC tokens in zkEVM operations while others are surprised by high fees: it is more expensive than that of the majority of competitors.
Introduced in 2021, Aztec is the first-ever ecosystem of L2 solutions focused on making Ethereum private as it unlocks the opportunities for both private and public smart contracts.
Aztec promotes itself as the first-ever hybrid ZK rollup. Actually, it is a combination of ZK layers: one layer of ZK infrastructure encrypts transactions to make them private and a second layer of ZK compresses transactions before sending them to Ethereum.
In 2022, it introduced Aztec Connect, the privacy-focused bridge solution for a couple of mainstream Ethereum dApps.
Aztec leverages Noir, its own smart contract language. Unlike all of its competitors, Aztec isn’t EVM compatible as it works outside Ethereum Virtual Machine.
The protocol leverages its own state tree based on unspent transactions output model (UTXO), a public state tree (that works not unlike Ethereum’s familiar Patricia-Merkle tree), and a zero-knowledge execution environment.
Aztec has an undisputed advantage over all competitors’ solutions: it prioritizes the privacy of all operations with smart contracts so that developers can integrate private state into their designs.
Aztec doesn’t support Solidity which is the most mainstream programming language for Ethereum-based dApps. Also, amidst accelerating regulatory witch-hunt all privacy solutions might be targeted by law enforcement units across the globe.
Not unlike Polygon zkEVM, Scroll is a zkEVM-based ZK rollup on Ethereum. It means that it remains 100% Ethereum-equivalent and is suitable for L1 dApps migration.
Introduced in 2021, Scroll inches to its mainnet release slowly but surely. Despite still being in the testing phase, it is already valued at over $1,6 billion after its latest funding rounds. Like other zkEVM products, Scroll prioritized EVM-equivalence as its main ‘killing feature’.
Scroll merges the benefits of all cutting-edge EVM developments. It is 100% equivalent to EVM ‘on the bytecode level’, it leverages familiar Solidity language, and therefore, makes migration from L1 to L2 more seamless and effortless than ever before.
First and foremost, it is equivalent to Ethereum. Then, it is fully VC-backed, so Scroll isn’t associated with a single market player that makes it more democratic and decentralized. Scroll is being developed by a team of high-profile Ethereum veterans.
Scroll is definitely lagging behind its rivals in zkEVM race: in early Q2, 2023, the product is still in Alpha Testnet Phase. So, it will take time to make it commercially viable. Its main competitors, Polygon zkEVM and zkSync have already proceeded to the next phases of development.
Best 10 ZK rollup projects of 2023: Upcoming products and go-to solutions
Besides the top league of ZK rollups, there are a number of promising solutions in development. Also, some leading dApps created their own ZK-based mechanisms.
Boba Network ZK rollup
Boba Network is the first-ever multi-blockchain L2 scaling solution on ZK proofs. It helps multiple EVM ecosystem blockchains - from BNB Chain to Moonriver - to scale through ZK rollups. Its zkBNB, a pioneering scaler for BNB Chain, stole the headlines in Q1, 2023.
Linea ZK rollup
Not unlike Polygon zkEVM, Linea is a zkEVM implementation by ConsenSys, a largest corporate entity of Ethereum scene. Besides being 100% EVM equivalent, Linea blockchain will be natively integrated with MetaMask, a most popular on-chain wallet and mainstream development tooling platform Truffle. As of May, 2023, Linea is available in public testnet.
Orbis ZK rollup
Orbis protocol is a first-ever ZK rollup for Cardano, a second-largest Proof-of-Stake blockchain. It leverages zkSNARK tech to scale Cardano as dApps interest in the blockchain accelerated.
The FTX collapse and related market uncertainty made the team stop the development: now the project is fully open-sourced and is supported by GitHub enthusiasts.
Taiko ZK rollup
Early-stage blockchain Taiko promotes itself as an Ethereum-equivalent ZK rollup. Its architecture boasts Proposers, Provers and Node Runners. Taiko prioritized EVM equivalence over the speed of generating ZK proofs. As such, it supports all Ethereum opcodes, but on L2 rails.
ImmutableX ZK rollup
ImmutableX is the first platform focused on real-world usage of L2 scaling technologies. Namely, it offers gasless minting of NFTs thanks to advanced scaling methodology. Its proprietary Immutable zkEVM is a ZK rollup chain tailored for the GameFi segment. It offers holistic EVM compatibility for blockchain-based games and metaverses.
Fox ZK rollup
Fox is an eccentric Ethereum ZK rollup that merges the benefits of zkEVM and its very own tech, Zero Knowledge-Fast Objective Argument of Knowledges abbreviated as ZK-FOAKS. It uses parallel computations and therefore paves the path for Layer Three solutions on the top of Ethereum. Fox uses Solidity and Rust programming languages.
Loopring ZK rollup
Loopring is among the oldest Ethereum scaling protocols: it offered first solutions for this challenge in early 2019. Now it promotes itself as a ZK rollup for payments and trading. Its tokenomical design is underpinned by LRC utility and governance token.
Ola ZK rollup
Ola is a first-ever L2 blockchain on Ethereum that is focused on programmable privacy. Simply put, it allows developers to choose whether this or that element of infrastructure should be public or private. Ola merges the benefits of UTXO model, ZKVM and ZK-ZKVM tooling.
Metis ZK rollup
Metis is arguably the cheapest rollup solution in the Ethereum ecosystem. It pioneers hybrid approach to rollups as it merges the benefits of ZK rollups and Optimistic Rollups, another method of scaling Ethereum. Metis brand-new Smart Layer 2 solution blends the privacy of ZK rollups with speed of Optimistic Rollups. With over $108 million in TVL, Metis Andromeda blockchain is the fifth largest L2 on Ethereum.
Mina ZK rollup
Mina is a privacy-focused blockchain on zkSNARKs. It isn’t built on Ethereum itself, but leverages its account-based model. Mina pioneered the concept of zkApps, i.e. blockchain applications that only work on the top of ZK networks.
How to build on ZK rollups: Shortest manual
In this segment, we’re going to demonstrate the shortest how-to on ZK-based dApps development. For instance, to develop a token on StarkNet, a blockchain engineer needs to follow some simple steps.
First of all, be sure you have an account on GetBlock, a top-tier blockchain node provider. GetBlock was among the first to launch StarkNet endpoints, so don't hesitate to use it for free while building your first StarkNet-based contracts.
Set up a development environment: Ensure you have a development environment with the necessary tools. This typically includes Node.js, NPM (Node Package Manager), and a code editor of your choice.
Install StarkNet SDK: Use NPM to install the StarkNet SDK, which provides the necessary tools and libraries for interacting with StarkNet. You can install it by running the following command in your terminal:
npm install --global starknet-sdk
- Create a new project: Initialize a new project using the StarkNet SDK. Run the following command to create a new project directory:
starknet-sdk init getblock_starknet_token
Write contract code: Inside your project directory, navigate to the contracts folder. You'll find a sample contract file named contract.cairo. Open this file in a code editor and define your token's contract logic using Cairo, the programming language used for StarkNet contracts. Implement features such as token transfers, balances, and other relevant functionality.
Compile the contract: Once you've written your contract code, you need to compile it into a StarkNet-compatible format. Use the StarkNet SDK to compile the contract by running the following command
starknet-sdk compile contracts/contract.cairo
This will generate an output file with a .json extension, representing the compiled contract.
Deploy the contract: To deploy the compiled contract to StarkNet, you need to interact with a StarkNet deployment provider. One option is to use the StarkNet Studio, which provides a web-based interface for deploying and interacting with contracts. Alternatively, you can use the StarkNet SDK's deployment tool. Run the following command to deploy your contract:
starknet-sdk deploy compiled/contract.json --network NETWORK_NAME
Replace NETWORK_NAME with the appropriate StarkNet network you wish to deploy to (e.g., "mainnet" or "ropsten").
- Interact with the token: After deploying the contract, you can now interact with the token on StarkNet. Use the SDK or any other suitable tool to send transactions, query balances, and perform token transfers based on the functions you implemented in your contract.
ZK rollups in 2023: FAQ
To sum up the content of this review, let’s answer the most common questions asked by newcomers about the ZK rollups segment.
How does ZK rollup differ from other scaling technologies?
In general, it offers different ways of broadcasting compressed transactions to Ethereum mainnet. Optimistic Rollups assume that every proof is correct while ZK rollups verify every piece of cryptographic data.
What are the key benefits of using ZK rollup?
It significantly (by 100x minimum) reduces the costs of Ethereum usage while the same level of security and decentralization is retained.
How do ZK rollup projects ensure security and privacy?
By sophisticated cryptography methodics, data about the transactions is encrypted. It is absurdly difficult to try to guess what is written in the message protected by modern ZKP technique.
What are the most promising ZK rollup projects to invest in?
All ZK narrative products are early-stage, so their native tokens are vulnerable to increased volatility. However, MINA, MATIC, and some other ZK tokens rallied in Q1, 2023. Also, STRK, ZKS airdrops are expected by communities.
What are some potential risks and limitations of using ZK rollup?
Mostly, analysts and users are concerned about the costs of ZK proofs generation and the centralization of Provers, i.e. key verification mechanisms in ZK rollups.
ZK rollups are second-layer networks on the top of Ethereum and EVM-compatible blockchains. They process transactional data off-chain to increase the capacity of Ethereum mainnet.
ZK rollups use zero-knowledge proofs to protect the integrity of data broadcasted to Ethereum.