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01 What is Rollup
Rollup, as the name suggests, means to summarize and organize.
In the Ethereum network, due to the bandwidth of the ETH network, the Gas fee will often increase significantly when the network transactions are more congested. The cost of one transaction is very high, sometimes even reaching tens or hundreds of dollars, and the speed is very slow.
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Every transaction in Ethereum contains data, and each data will consume gas, because the Ethereum network sets the upper limit of the amount of data per block and the upper limit of TPS. So, how do we increase the capacity, speed, and TPS of Ethereum without transferring all content data to offchain? Rollup comes out
The role of Rollup is to copy the content that needs to be calculated by Ethereum and send it to the Layer 2 protocol connected outside of Ethereum for calculation. Then, the result information is compressed and packaged, ready to be sent, and sent back to the on-chain network.
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It's like everyone has 1 question, but it's time-consuming and labor-intensive to present one by one. The selected and trusted representatives are used to summarize and review everyone's problems and deal with them in a centralized manner, thus greatly improving efficiency. 1 means that the question has been answered, which means that 100 questions are OK.
Part of the data on the chain remains unchanged. Therefore, the reliability of the representative in the middle (Rollup Layer 2 protocol) also determines the security of Ethereum. Different Rollup models have different styles and advantages and disadvantages.
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02 What is ZK Rollups
ZK Rollups,ZKSnark or Zero Knowledge Rollups, as the name suggests, performs Rollups through zero-knowledge proof verification. Zero-knowledge proof is also one of the main contributions in cryptography by Silvio Micali, the founder of the blockchain public chain project Algorand.
The four major characteristics of ZK (note that ZK is not JK):
Zero Knowledge: Verifiers do not need to see data on the trading platform
Succinct: succinct, succinct
Non-Interactive: No need to know who the validator is
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Therefore, the core method of Zk Rollups is to verify the authenticity (Validity Proof) of different data through rigorous and complex verification algorithms, and the verifier (ZkSnarker/Validator) in the Layer 2 protocol, thereby packaging the verification results. After the Ethereum network eliminates redundant work information, it can directly absorb data blocks with a large amount of compressed signature information into the network.
Anyone can participate in network authentication and become an authenticator, so, in essence, ZKSnark is also a Layer 2 protocol of PoW consensus mechanism.
【advantage】:
Layer 2 is verified by Ethereum very quickly, and assets stored in Layer 2 can be quickly withdrawn back to Layer 1 Ethereum
It is very suitable for applications that require fast settlement, such as payment, banks, and trading platforms
[Disadvantages]: Due to the complexity of the algorithm, it is a bit difficult for application development
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03 What is Optimistic Rollups Layer 2
The Optimistic method is as its name implies: Optimistic, starting to think that all sent transactions are trustworthy and certified,
The Layer 2 verifier needs to pledge Token as a deposit first. If someone finds a problematic package during the verification process, the verifier (Sequencer) will be fined part of the Token and rewarded to the person who found the problem.
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Optimistic Rollups also has smart contract functions and can have corresponding governance tokens,
The essential difference between Op Rollups and ZK Rollups is that everyone in ZK can participate in the certification through PoW certification, while OP is more inclined to select a group of trustworthy authenticators to supervise the entire packaging transaction process.
【advantage】:
1. It is suitable for developing Dapp, which can almost seamlessly migrate the original project in Layer 1, and is also developing the corresponding OVM virtual machine
【shortcoming】:
The withdrawal speed of Layer 2 to Layer 1 is relatively slow, and usually takes more than 1 week (because the verifier needs to verify the authenticity of the package), but there are currently optimized supplementary protocols to help speed up the speed of this model.
There is a risk cost for verifiers to do evil.
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04 What is Arbitrum
First of all, as mentioned earlier, Arbitrum is essentially a Layer 2 protocol project that utilizes the Optimistic Rollup model. Often used for comparison with the Opitmisim project, the current TVL at the Layer 2 level is the highest among many protocols. When the OP project is certified, it only conducts one round of fraud proof, and the transaction calculation of Layer 2 relies on Layer 1 to execute.
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summary:
This article tries to use easy examples to explain several hot concepts that confuse many friends around me, including the author himself who has been troubled by various OP, ZK series projects and methodologies. After thinking and explaining with examples, I hope that everyone can have a clearer concept and technical hobbies. You can also consult the engineers who develop the corresponding protocols. In order to preserve some brain cells, this article will not elaborate on the technical details. Finally, tidy up:
Rollup refers to a sorting method that sends a bunch of transaction tasks to the Layer 2 protocol to work, thereby improving the operating efficiency of Ethereum.
Zk Rollups refers to a Layer 2 method that uses zero-knowledge proof cryptographic algorithms to complete outsourcing work without knowing who the verifier is.
Optimistic Rollups refers to a Layer 2 method that uses a bunch of verifiers to monitor whether there are bugs through a reward and punishment mechanism when the default packaging is good.
Both Optimism and Arbitrum are projects based on the Optimisctic Rollups method.
Zksync,ZKxxxxxxxx Many ZK projects are developed based on the ZK Rollups method or as a gimmick.
The current ZK Rollups are more suitable for Payment, and other businesses that require fast transactions, and the algorithm is slightly more complicated; while the Optimistic method is more suitable for Dapp development and Defi business, but the withdrawal time is a bit long.
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