I studied @VitalikButerin’s new work on the return of Plasma and used UTXO-like ledgers to implement the “exit game” mechanism, which aroused the author’s interest. The author believes that Vitalik is also guiding the market to explore in the direction of ZK+Plasma to avoid the market staying in the Rollup stage.
1) The reason why Plasma chain is suitable for payment scenarios is that it has high scalability and low transaction costs. The Plasma chain reduces the burden on the main chain by outsourcing part of the transactions to the side chain, thereby achieving higher transaction throughput. At the same time, the Plasma chain adopts a UTXO-like model to ensure the security and correctness of the ledger, making payment transactions more secure and reliable.
2) The operation mode of Plasma payment scenario is based on UTXO-like model. Users first lock funds into a contract on the main chain, and then conduct fast and cheap transactions on the side chain by creating Plasma channels. Transactions that occur within the channel are not submitted to the main chain in real time. Instead, when the channel is closed, the final status is submitted to the main chain for settlement. This method ensures high throughput and low cost of payments.
3) The exit game mechanism is very important to Plasma because it solves the security issues in sidechains. The exit game mechanism allows users to safely exit the side chain and retain their correct asset status when abnormal behavior is discovered in the side chain. This mechanism ensures the security of users’ assets and prevents evildoers from manipulating the asset status of the side chain.
4) Plasma chain is difficult to integrate the ownerless state of EVM, mainly because of the limitations brought by the UTXO-like model. Since the design goal of the Plasma chain is to achieve high scalability and low transaction costs, in order to improve efficiency, the Plasma chain ignores the functions related to account state conversion in the EVM and adopts a more simplified UTXO model, which results in the inability to directly Integrated EVM's masterless state.
5) ZK+Plasma can release a lot of imagination. ZK stands for zero-knowledge proof, which can help verify the correctness of transactions without revealing specific transaction information, which brings higher privacy and security to the Plasma chain. The combination of ZK+Plasma can provide more possibilities for achieving scalability, privacy and security, such as realizing more advanced smart contracts, cross-chain interoperability, protecting user privacy, etc.
Plasma is currently limited to payment scenarios, partly because its original design was to solve the expansion problem in payment scenarios. Through the UTXO-like ledger model and the side chain method, the Plasma chain can achieve high scalability and low transaction costs, and has certain advantages in payment scenarios. But at the same time, the design of the Plasma chain also has certain limitations. For example, as a side chain, data synchronization between the main chain and the side chain is an important issue. If the synchronization is not timely or there are centralized dependencies, it may affect Security and performance. In addition, although the Plasma chain has certain smart contract capabilities, it still has certain limitations compared with the Ethereum main chain. Therefore, the Plasma chain is still mainly focused on payment scenarios, but it may still expand to other areas in the future.
Indeed, the use of Plasma in payment scenarios can ensure that the ledger status is effectively tracked and recorded. This is mainly because Plasma adopts a UTXO-like model and retains the account balance status. Compared with other scenarios that require retaining all off-chain state data, the use of the UTXO model can reduce the pressure on storage space and also improve the efficiency of transactions. The Plasma chain relies on the "exit game" mechanism in terms of security. If the operator does evil, users can initiate a challenge and submit their own assets to ensure the correctness of the asset status. However, if the asset status is very complex, the cost and complexity of generating proof will also increase accordingly, thereby reducing the operating efficiency of the system. In addition, it is currently difficult for Plasma to be compatible with many unowned states of EVM. It is difficult for users to use Plasma’s Merkle state tree ledger to correspond to many non-transaction states, such as LP and CDP. This is also an obvious limitation on the application of Plasma in other fields. The problem. In the Plasma payment scenario, the way it works is using Plasma Cash. Plasma Cash treats each Token as a non-fungible token (NFT), and each Token has a unique number. When a user makes a transfer, the operator records an updated status in the Merkle tree. Each user can save his or her own global Merkle tree state, so that changes to the ledger can be accurately traced and data consistency ensured.
For homogenized Tokens, how to solve the problem of Merkel data redundancy that may be caused by multiple splits and mergers? A UTXO-like ID can be matched for each asset split or merge status, so that the corresponding transaction leaves can be immediately located no matter how the asset is split, thus avoiding data redundancy and high cost of challenge verification.
Regarding security and exiting the game mechanism, since Plasma does not have an independent chain system like Rollup, it needs to ensure that its side chain accounting and the main network are synchronized. Therefore, the operating entity in the Plasma payment scenario does not need to pursue complete decentralization. As long as there is an operating entity that can efficiently keep accounts, the implementation of the safe exit game mechanism can be ensured. Indeed, if the operator releases invalid blocks, records false accounts, or steals user assets, it will threaten the security of the Plasma payment scenario. In order to deal with these problems, the "exit game" mechanism was introduced in the Plasma payment scenario.
Users can withdraw assets on level 2 back to level 1 through the "exit game" mechanism, similar to Rollup's escape hatch safety mechanism. The specific method is that users can post their Merkle tree status certificate to prove the asset transfer process and initiate a 7-day challenge period. The main network verification node will detect whether the user is the final asset owner and whether the user has problems such as double spending of assets. Since the main network node stores more Merkle tree states, the user's Proof can be checked for malicious exits.
Through the "exit game" mechanism and the existence of the challenge period, layer 2 operators can be effectively restrained from doing evil and users can be prevented from maliciously exiting, thereby ensuring the normal operation of the Plasma chain and the security of assets. Indeed, Plasma is difficult to be compatible with the "ownerless state" in EVM, which is a difficulty. Because Plasma is an accounting model that can be compared to the UTXO model, and EVM is an account model. In the UTXO model, each balance status refresh can be recorded, but many "Owner-less" scenarios in the EVM state machine are difficult to implement using Plasma's solution.
For scenarios such as USDC deposited in the Uniswap pool and assets placed in MakerDAO's CDP, it is difficult for users to prove which assets belong to them. Once the operator goes down and the contract is locked, users cannot "exit the game" normally. . Because there is no way to prove that the user has money in the contract, the main network can only monitor the balance of the contract. If the operator issues an additional amount of money to the contract, the user cannot prove which amount is his or hers and which amount was maliciously issued.
If a layer 2 side chain can only implement Payment transfer transactions, then building applications and ecosystems will be greatly restricted. Therefore, it is necessary to conduct in-depth research and solutions to these problems to overcome these difficulties, achieve compatibility with the "ownerless state" in EVM, and at the same time expand the usage scenarios of Plasma so that it can play a role in more application scenarios. If the bottom layer of Plasma is completely ZK-ified, user operations will exist in the form of zk-SNARK proofs, which will release many EVM state machine scenarios. For example, for an asset deposited by a user into a Plasma contract, a zkSNARKs certificate can be constructed and an "exit game" initiated to the main network. Even if the pool is frozen due to security threats, users can withdraw their legal assets. Therefore, the introduction of zk-SNARKs can improve the security of Plasma payment scenarios.
In transaction scenarios involving privacy DEX, users can use zk-SNARKs to prove that they own certain assets without exposing personal privacy, which also helps to improve the anonymity and privacy protection of transactions.
At the same time, when performing complex upgrades, Plasma's smart contracts can also use zk-SNARKs to provide correctness proof of their state upgrades without exposing details, which helps improve the security of the contract and reduce the possibility of evildoing. Therefore, the use of zk-SNARKs will help improve the security and flexibility of the Plasma chain and play the role of Plasm in more application scenarios.
Taken together, Vitalik clearly described the current situation and existing problems of Plasma in the article, and proposed possible ZK-oriented directions in the future. However, you argue that Plasma is not new and has already found its place in the payment scenario. You are not optimistic about the new direction of ZK+Plasma proposed by Vitalik.
Do you think that in the current market, Rollup, as a solution that comprehensively considers investment cost, development difficulty and ecological compatibility, has become the optimal solution. Although ZK+Plasma can be regarded as a more advanced ZK-Rollup, the current development of ZK-Rollup is not optimistic, and jumping directly to Plasma may be too hasty.
In addition, you mentioned that Validium is an independent chain expansion solution, and its application in ZK is relatively advanced. Although ZK+Plasma may be more sticky with the Ethereum mainnet, you think Vitalik's call is understandable, because mature ZK developers may have insufficient motivation to abandon Validium and choose ZK+Plasma. In short, you have reservations about the prospects of ZK+Plasma proposed by Vitalik and raised your views on the current market situation. Note: Please be sure to read Vitalik's article carefully and then understand this article. If you think my sharing is valuable, you are welcome to support it with one click and three consecutive clicks. Thank you.
Original link: https://vitalik.eth.limo/general/2023/11/14/neoplasma.html
