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Many people believe blockchain can transform industries ranging from finance to supply chains to healthcare and more. Yet despite being around for more than a decade, challenges continue to hinder blockchain’s adoption, with one of the most pressing ones being the problem of how to scale to support millions of transactions.
Looking to overcome this challenge once and for all, ZK-Rollups, or Zero-Knowledge Rollups, are an extremely promising concept that aims to dramatically increase the throughput of blockchains. ZK-Rollups are Layer-2 scaling solutions that take advantage of Zero-Knowledge Proofs to enable benefits that go beyond simply increasing throughput, giving users full privacy as well.
ZK-Rollups: The Basic Concept Explained
Zk-Rollups make use of a Layer-2 network that sits above the main blockchain, where transactions can be offloaded and bundled together before being processed as one, massive transaction, back on the main chain. They make use of ZK proofs to obscure transaction details, verifying their accuracy using a “validity proof” that’s submitted to the main chain. In this way, they reduce the overall load on the main chain, enabling it to process many more transactions. Another benefit is significantly lower gas fees, as these costs are split across all of the transactions bundled together.
The secret sauce of ZK-Rollups is the zk-SNARK, or Zero-Knowledge Succinct Non-Interactive Argument of Knowledge, which is a cryptographic technique that makes it possible for one party to prove to another that a transaction is accurate, without revealing any details of that transaction.
In a nutshell, ZK-Rollups work like this:
- The users submit their transaction to the ZK-Rollup contract
- The operator process these transactions off-chain before aggregating them into batches
- It then generates a validity proof for the entire batch using zk-SNARKS
- This proof, along with the end state of the Rollup after all transactions have been processed, is submitted to the mainnet
- The mainnet verifies the validity proof and updates all of the wallets involved in that batch of transactions.
- Finally, users can then withdraw their funds from the rollup smart contract
The Advantages Of ZK-Rollups
ZK-Rollups provide significant advantages over older scaling techniques such as sidechains and “Optimistic Rollups” that currently lead the way on Ethereum.
Just like ZK-Rollups, Optimistic Rollups also process transactions off-chain and bundle them into batches to submit to the relay chain. But rather than using ZK-proofs, they use a fraud-proof mechanism in which transactions are assumed to be valid, unless someone challenges them. This necessitates the use of a “window” or period of time in which anyone is free to check and verify the transactions, and issue a challenge if they discover someone is cheating. Should the challenge be successful, the fraudulent transaction is rolled back, and the challenger earns a reward.
Sidechains are an alternative. They are independent blockchain networks that run in parallel with the mainnet, using their own consensus mechanisms that allow them to process transactions by themselves. They connect to the mainnet using a “two-way peg”, which enables the transfer of assets between the two chains.
ZK-Rollups provide compelling advantages over Optimistic Rollups and Sidechains:
- Increased transaction finality compared to Optimistic Rollups, because the use of ZK-proofs means they can be verified instantly upon submission to the mainnet. The challenge period with Optimistic Rollup means that transactions will always be delayed.
- Greater security compared to Sidechains because they inherit the security of the underlying mainnet through their use of validity proofs. Sidechains rely on their own security models, which are much weaker than established blockchains like Ethereum.
- Reduced gas fees are another benefit of ZK-Rollups compared to Sidechains. Because many transactions are aggregated into one, which is then processed on the main chain, the gas fee paid to Ethereum can be shared across all of the transactions in the bundle. Sidechains cannot do this. They still process each transaction independently, which means the user pays the entire transaction fee.
What’s The State of ZK-Rollups?
Several projects are bringing ZK-Rollups to the mainstream. One of the most promising is the modular zkEVM Layer-2 network, Prom ZkEVM, which has created a solution that supports Ethereum, EVM-compatible blockchains and non-EVM blockchains.
This extensive support is essential for Prom ZkEVM, as it is on a mission to deliver interoperability across all major blockchains. Its architecture allows it to simultaneously submit validity proofs to two blockchains at once.
Prom ZkEVM’s use of recursive STARK technology has proven itself to be both extremely scalable and highly economical, while its high degree of interoperability makes life simple for Web3 developers. What’s more, it also supports “account abstraction” features enabled by the ERC-4337 standard, so dApps can implement user-friendly features such as traditional, email-based account recovery methods.
zkSync is another big name in the ZK-Rollup space. As one of the earliest ZK-Rollup implementations, it has a significant first-mover advantage that has helped to propel its adoption, winning over hundreds of dApp developers with its promise of 2,000 transactions per second.
These impressive speeds are backed by strong security, which zkSync inherits from Ethereum, and low transaction fees. What’s more, many developers consider zkSync’s mature rollups easier to implement, meaning dApps can support frictionless asset transfers across EVM chains without any latency.
More specialized ZK-Rollups such as Immutable X are focused on niche use cases within Ethereum, such as Web3 games. It’s targeted at blockchain games that utilize NFTs as in-game characters, weapons and accessories. In many games, these assets are extremely inexpensive, so there’s a need to keep transaction fees to a minimum. This is why Immutable X is favored by hundreds of blockchain games. It enables players to instantly buy and sell low-cost assets with negligible fees.
In addition, blockchain games players need to be able to transact instantaneously. They want to be able to buy a new gun or item and use it immediately in their next game. Immutable X does this, boasting an incredible speed of 9,000 transactions per second. As an added benefit, Immutable X says NFTs on its network are carbon neutral thanks to its highly-efficient, proof-of-stake consensus mechanism.
Blockchain Scalability Achieved
The progress of projects like Prom ZkEVM, zkSync and Immutable X demonstrates how ZK-Rollups have achieved the level of maturity required for the technology to go mainstream. ZK-Rollups offer more than just promises – they are actively transforming blockchains, allowing them to achieve scale while enhancing the security and privacy of every user.
By utilizing the cutting-edge capabilities of ZK-proofs, ZK-Rollups provide dApps with a powerful, versatile, secure and privacy-preserving way to scale on any blockchain.