Zk rollups: How to join the zero-knowledge movement and scale Ethereum to the next level

It can process thousands of transactions in a batch and then post minimal summary data to Mainnet.

The technology behind zk-rollups relies on zero-knowledge proofs, a cryptographic technique that allows one party to prove the validity of a statement without revealing any additional information.

What are zero-knowledge proofs? What does zero mean?

Zero-knowledge proofs are a way of proving that something is true without revealing any information about it. The "zero-knowledge" part of the name refers to the fact that the proof does not reveal any information beyond the statement's validity.

Example: The Ali Baba cave

Suppose you want to prove to your friend that you know the magic word to open a secret door in a cave. The cave has two entrances, A and B, that lead to the same point where the secret door is located. You can only open the door inside the cave by saying the magic word. You don't want to tell your friend the magic word or show him the door.

A zero-knowledge proof method for this problem would be like this:

• You enter the cave from either entrance A or B while your friend waits outside.
• Your friend then chooses an entrance and calls it out to you.
• You come out of the entrance that your friend chose, proving that you can open the door from the inside.
• Your friend is not convinced. You have a 50% chance to enter the cave from the same entrance your friend will choose and come out without opening the door.
• However, if you repeat this several times, eventually, the probability of you coming out of the same entrance that your friend chooses each time would be very low. This convinces your friend that you know the magic word without revealing it or showing him the door.

Zero-knowledge proofs are useful for preserving privacy and security in many applications, such as authentication, cryptography, blockchain, and more.

There are different types of zero-knowledge proofs, such as interactive and non-interactive. Interactive zero-knowledge proofs require communication between the prover and the verifier, while non-interactive ones do not. The above scenario of Alibab cave is an example of interactive ZKP.

The Technology behind zk-rollups:

• Zero-knowledge proofs (ZKPs): ZKPs allow one party to prove the validity of a statement without revealing any additional information. In the context of zk-rollups, ZKPs are used to prove the validity of bundled transactions without revealing their details.
• zk-SNARKs: A specific type of ZKP, zk-SNARKs are compact and efficient proofs that can be verified quickly. They are used in zk-rollups to create a single proof for multiple transactions.

What are the advantages and disadvantages of zk rollups?

• Scalability: By bundling multiple transactions into a single proof, zk-rollups significantly increase the transaction throughput of a blockchain.
• Reduced gas fees: As the main chain only needs to verify a single proof instead of individual transactions, gas fees are reduced.
• Security: Zk-rollups inherit the security of the underlying main chain, as the main chain verifies the zk-SNARKs.
• Privacy: Zero-knowledge proofs can provide a level of privacy by hiding transaction details while still proving their validity.

• Complex technology: Zk rollups rely on advanced cryptography and mathematics that are difficult to understand or implement.
• Limited functionality: Zk rollups are currently optimized for token transfers and simple operations but not for complex smart contracts or general computations.
• High upfront costs: Zk rollups require a lot of computational resources and gas fees to generate and verify the proofs, which can be expensive and time-consuming.

Some examples of zk rollup projects