Author | @tmel0211 Share｜Baidu Blockchain (ID: hellobtc)
Perhaps everyone is used to the ridiculously expensive gas fee of $0.7 per transaction for ARB and OP, which is not at all the low cost that L2 should have. In the spirit of hardcore popular science, let's analyze the difference between zk-rollup and op-rollup? And the reason why the current zkSync gas fee is relatively high. When it comes to the ZK track, many people blurt out zero-knowledge proof, which is easily linked to privacy protection features. However, the mainstream discussion of zk-rollup is actually to solve the scalability problem, using SNARKs and STARKs proof technology to implement validaor proof, that is, verifier proof. The zero-knowledge privacy protection feature has a weak presence in zk-rollup. Let's ignore the concept of privacy and think about the technical principles behind it from the perspective of "verifier proof". Simply put, all transactions in zk-rollup occur on the side chain, which is equivalent to using the zk technology algorithm off-chain to package these transactions into batches, and generate SNARKs proofs and submit them to the main network. The main network smart contract will verify whether all transactions in the batch comply with the rules through the zk algorithm, and then package them on the main chain. This greatly expands the transaction capacity and transaction speed of the main network, while intersecting the main chain reduces gas consumption.
The logic of op-rollup is easier to understand. A large number of transactions are submitted to the side chain for calculation and packaging, and then the ledger results are aggregated into a block and synchronized to the main network smart contract. In order to prevent validators from doing evil, fraud proof technology is used. That is, if a validator submits a suspicious transaction and is confirmed within 7 days, the entire block will be rolled back, thereby ensuring the security and integrity of the transaction. The difference between zk-rollup and op-rollup is essentially the two verification methods of validator proof and fraud proof.
Although the validator proof method consumes more computing power and resources to verify transactions, it can ensure the accuracy of the results within the block cycle, thereby increasing the speed of transaction processing. Op-rollup uses the fraud proof method, which saves resources but requires a period of waiting. It is worth mentioning that op-rollup uses time in exchange for cheaper resources and consumption, but its side chain server has certain centralization risks, such as sequence sorters. zk-rollup uses short-term resource and computing power consumption in exchange for shorter security confirmation time, and technologies such as account abstraction and distributed verification avoid centralization risks. Therefore, the high gas fee of zk-rollup is understandable, and the two are not comparable at all. The current transaction fee of zkSync depends on three aspects: (1) The resource cost consumed by the validator to generate SNARK proofs and verify them, such as storage and computing; this part of the fixed cost is relatively high; (2) The gas fee when the validator submits the SNARK proof to the Ethereum mainnet. This part of the fee will increase accordingly due to mainnet congestion. (3) The service fees paid by users to the validator, including transaction confirmation, message broadcasting, etc., must cover the above fees. In general, L2 user gas fee = zk system computing and storage resource fee + each batch submitted to the main network gas fee + validator node incentive fee + other?
There is no need to say much about the mainnet gas fee and node incentive fee. Since the cost of computer resources is relatively fixed and the more people there are, the more diluted it will be, which means that with the further mass adoption of zkSync, the gas fee will drop. Yes, the current high gas fee is not because it is too high, but because it is not high enough!!
According to @DuneAnalytics data, the average daily transaction volume of zkSync is about 100,000-400,000 times. Although the majority of people are still interacting with it, compared with the ultimate goal of zk-rollup, the zksync ecosystem is still an alpha baby. Why not stop complaining about high gas and continue building together?
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