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Easy understanding of Rollup: The difference between ZK Rollups and Optimistic, Arbitrum

2023-02-13 15:19

Read this article in 14 Minutes

The differences between Rollups.

原文标题：《轻松理解 Rollup, ZK Rollups 与 Optimistic，Arbitrum 的区别》

Future Little brother

01 What is Rollup

Rollup Rollup rollup

In the Ethereum network, due to the ETH network bandwidth, Gas costs often increase significantly when there are a lot of traffic on the network. The transaction cost is very high, sometimes even tens of hundreds of dollars, and the speed is very slow.

This is similar to our weekday meals, and holidays in tourist attractions to increase the queue time and price increase (usually a loaf of 5 pieces, garden peak selling you 50); Or through the highway intersection toll booth weekdays and holidays the same difference.

Each Ethereum transaction contains data, and each data consumes gas, since the Ethereum network sets a cap on the amount of data per block, as well as a cap on TPS. So, how can we increase the capacity and speed of Ethereum, TPS, without moving all the content data to offchain? Rollup comes out

Rollup's function is to Copy the content that Ethereum needs to compute and send it to Layer2 protocol connected outside Ethereum for computation. Then, the resulting information is compressed, packaged, ready to be sent back to the on-chain network.

In the compressed block, there are a lot of signature confirmation information. Previously, there was only one confirmation Sign signature in a Block for each transaction on the chain, but now this block is equivalent to a VIP signature block with many transaction signatures compressed. One VIP passed is equal to 100 passed. This will indirectly increase the TPS of ETH substantially.

It's like everyone has a question, but presenting it to each meeting takes time and effort. By having elected, trusted representatives to review and address all of your problems, we have greatly increased efficiency. One means you're done, which equals 100 questions.

Part of the data on the chain remains unchanged, so the reliability of the representative in the middle (Rollup Layer 2 protocol) also determines the security of Ethereum. Different Rollup modes also produce different styles and advantages and disadvantages.

So, just a quick primer on the superficial differences between Optimistic and ZK Rollups, a few representatives:

02 What is ZK Rollups

ZK Rollups, ZKSnark, or Zero Knowledge Rollups. As the name suggests, Rollups is performed by proof of zero knowledge. Zero-knowledge proof is also one of the major contributions of Silvio Micali, founder of blockchain project Algorand, to cryptography.

Four features of ZK (note that ZK is not JK) :

Zero Knowledge: The verifier does not need to see that the trading platform has data

Inside the house, it was Succinct

Non-Interactive: You don't need to know who the verifier is

Argument of Knowledge: Prove the authenticity and correctness of the transaction

Therefore, the core method of Zk Rollups is to authenticate the Validity Proof of different data through rigorous and complex verification algorithm, ZkSnarker/ Validator in Layer 2 protocol, thus packaging the authentication results. The Ethereum network can absorb blocks of data containing large amounts of compressed signature information directly into the network after eliminating excess working information.

Anyone can participate in network authentication and become a certifier, so in essence, ZKSnark is also a Layer 2 protocol of PoW consensus mechanism.

【 Advantages 】 :

Layer2 can be verified by Ethereum very quickly, so assets stored in Layer2 can be withdrawn back to Layer1 Ethereum very quickly

It is suitable for Payment, bank, trading platform and other businesses that need quick settlement

[Disadvantage] : Because the algorithm is more complex, it has a threshold for application development

However, ZK is still the most valuable long-term scaling method if a more algorithm-based DApp-friendly model can be developed in the future

Optimistic Rollups Layer2 What is Optimistic Rollups Layer2

Optimistic is as optimistic as its name suggests: optimistic, begins to believe that all transactions sent are trustworthy and verified,

The Layer 2 verifier needs to pledge the Token as the deposit first. If others find the defective package during the verification process, this Sequencer will be fined part of the Token and give it as a reward to those who find the problem.

After each data packaging, there is a validation period for other verifiers to check if there is a problem and if the packaging needs to be returned.

Optimistic Rollups also has smart contracts and can have governance tokens accordingly,

The essential difference between Op Rollups and ZK Rollups is that everyone in ZK can participate in the certification through PoW certification, while OP prefers to select a group of trusted certificators to oversee the entire package transaction process.

【 Advantages 】 :

1. Suitable for the development of Dapp, the project originally in Layer1 can be migrated almost seamlessly, and the corresponding OVM is also being developed

【 Disadvantage 】 :

The speed of Layer2 to Layer1 is relatively slow, usually taking more than 1 week (because the verfier needs to verify the authenticity of the package), but currently there are optimized supplementary protocols to help speed up this mode.

There is a risk cost of the verifier doing evil.

We often use to talk about OP Token. Optimism is one of Layer2 protocols using Optimistic method, while Arbitrum is also a Layer2 protocol developed using Optimistic Rollups model. Because of the very similar name for the Opitmism project and Optimistic Rollup method, it can be very confusing.

04 What is Arbitrum

First, as mentioned earlier, Arbitrum is also essentially a Layer 2 protocol project utilizing the Optimistic Rollup model. Often used for comparison with Opitmisim projects, currently TVL on the Layer2 layer is the highest among many protocols. When OP projects are authenticated, only one round of fraud proof is performed, and the transaction calculation of Layer 2 depends on Layer1.

When Arbitrum verified, the fraud proofs. Aribitrum, meanwhile, does not run transactions on Layer1 and has its own virtual machine, which is more compatible with ETH networks.

Summary:

This article tries to use light examples to explain a few hot concepts that confuse many people around me, including the author himself has been troubled by various OP, ZK series projects and methodology. After thinking and the explanation of examples, I hope to let you have a clearer concept, the technical level of the hobby, you can also consult the corresponding protocol development engineers, in order to retain some brain cells, this article will not elaborate on the technical details. One last tidbit:

Rollup refers to a collation method that sends a bunch of transaction tasks to Layer2 to make Ethereum more efficient.

Zk Rollups refers to a Layer2 method that uses a zero-knowledge proof cryptography algorithm to perform outsourced work without knowing who the verifier is.

Optimistic Rollups is an Optimistic Rollups method of Layer2 that uses a group of verifiers to monitor the detection of bugs through a reward and punishment mechanism if the default packaging is good.

Optimism and Arbitrum are both projects developed based on the Optimisctic Rollups method.

Zksync, ZKxxxxxxx Many ZKS are developed based on the ZK Rollups method or gimmicks.

The current ZK Rollups is more suitable for Payment and other businesses requiring fast transaction, and the algorithm is slightly complex. Optimistic method is more suitable for Dapp development and Defi business, but the withdrawal time is a little long.

Other Layer2 protocols, Plasma, Metis, and Truebit, which uses game mechanics and AI, are all exploring optimal solutions to Ethereum's capacity expansion.

Note: This article is for popular science purposes, no investment advice, please judge rationally, reprint the article, please indicate the source of the author, if reprint on Twitter, please @santili1021