A Zero-Knowledge Rollup or ‘ZK-Rollup’ is a Layer 2 scaling solution that uses zero-knowledge proofs to speed up and reduce the costs of transactions on the blockchain.

A rollup processes transactions outside the main blockchain, or mainnet, in batches, then records a summary of each batch on the blockchain as a single transaction. By compressing the data, transactions take up less space on the blockchain. Also, by rolling up many transactions into one, the blockchain can handle more transactions per second while saving on gas fees.

A ZK-rollup is a special type of rollup that is controlled by smart contracts and uses zero-knowledge proofs, which are protocols that allow a person to prove the truth of a statement without sharing the statement's contents or revealing how one discovered the truth. After processing transactions off-chain, a summary of the transactions as well as proof of their accuracy is sent back to the main blockchain. 

With this, the blockchain network only needs to verify the proof to be able to record the data.

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Benefits of ZK-Rollups

• Higher security compared to optimistic rollups, which simply accept new data without a verification process.
• Lower gas fees because a whole batch of transactions will only require the transaction fee to be paid once.
• Less congestion in blockchain networks since transactions are processed faster.
• Increased privacy since the contents of the transactions do not have to be recorded publicly.

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Limitations of ZK-Rollups

• ZK-rollups are complex and time-consuming to compute.
• Since transactions are processed off-chain, there is a chance that they may be vulnerable to security attacks before they are sent to the mainnet.

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Zero-knowledge rollups are an effective way to increase the capacity of a blockchain network while maintaining its accuracy and security. As more industries begin to adopt blockchain technology, we can expect to see more projects using zero-knowledge proofs.