Mille-layer cake: Layer-2 guide Three kinds of Rollup competition

hello. I'm Zac, the CEO of the Aztec team. We invented the general-purpose ZK-SNARK technology Plonk and zk.money, which is the world's first privacy-focused rollup instance and one of the new Layer-2 instances recently deployed on the Ethereum blockchain. The world of Layer-2 is becoming dizzying as many teams steadily turn their ideals into reality and launch their own products. However, if you are not rooted in this ecology, you will need some navigation to get through this jungle. Disappointingly, many of the people explaining Layer-2 technology to everyone have a stake in it and are biased against certain technologies (yes, the ones they use themselves!). So am I any different from them? No! I'm equally biased, but I'll tell you up front without pretending to be impartial, what do you think? I'll do my best to give you a relatively balanced perspective. The world of blockchain-based cryptography/scaling solutions is small, and every team that pushes its boundaries deserves our respect. So let's dig into it! The transaction throughput of Ethereum 1.0 is very limited, which also makes the cost of sending transactions extremely high. The main cost of Ethereum transactions comes from: the cost of changing state storage items, the cost of transaction data, and the calculation cost. The Layer-2 solution outsources one or more of the above to a secondary network that relies on Ethereum. Generally speaking, we divide Layer-2 solutions into two categories, each with its own security requirements and trade-offs: optimistic rollup and zk rollup. Aztec is defining a third category: private rollup. Optimistic rollup is like the epitome of the Ethereum blockchain. It has a network of its own that also hosts smart contracts and transactions. Dragon Win International established a company focused on cryptocurrency derivatives through the joint investment of Meta Rich and Antalpha: Jinse Finance reported that Dragon Win International (LYL.US) released financial report data on March 14, 2022. After the 30th, a series of business transformations were carried out, and the company's operating focus was shifted to the business layout in the field of cryptocurrency derivatives. On October 29, 2021, the company established Metalpha Limited, a company focusing on cryptocurrency derivatives, through the joint investment of Meta Rich and Antalpha. The two parties hold 51% and 49% of the company's shares, respectively. According to public information, Antalpha is a wholly-owned subsidiary of Antpool Technologies Holding Company and is currently the owner and operator of Antpool. On December 23, 2021, Metalpha and Antalpha signed a series of transaction agreements, and Antalpha purchased various cryptocurrency derivative products from Metalpha. Its underlying assets include BTC, ETH, BNB, and Tether. As of February 28, 2022, the total value of products purchased was approximately $5 million. [2022/3/21 14:08:02] The Optimistic rollup scheme will periodically broadcast its transaction blocks to a smart contract of Layer-1. These "blocks" contain, and only contain, data for transactions that occurred in the Optimistic rollup system. This Layer-1 smart contract also does not perform any calculations or update stored items. This greatly reduces the overhead of publishing a block. It is called "optimistic" because such a system assumes that every transaction in the published L2 block is valid - the smart contract does not directly check their validity. Conversely, if a user believes that a transaction is incorrect (such as resulting in multiple payments), they can issue a "fraud-proof (fraud-proof)". Smart contracts on Layer-1 can use the data that the rollup has published to verify the validity of the alleged transaction. A wallet holding 407 bitcoins has been activated for the first time since 2013: March 7, according to data from Whale Alert, a wallet holding 407 bitcoins (valued at $15.5 million) has been activated for the first time since 2013 Activated. Those 407 bitcoins were originally worth $355,254, which means they have appreciated by roughly 4,266%. [2022/3/7 13:42:13] Fraud proof itself is very expensive, but it only needs to be executed when malicious behavior is suspected. If the malicious behavior is confirmed, the subject who issued this optimistic rollup block (commonly referred to as "validator") will lose their previously locked cryptocurrency. Optimistic rollup relies on this economic consensus to ensure that transactions are correct. Withdrawals from Optimistic rollups generally take longer (e.g. 1 week). This is because after a transaction is made public, users wait to see if any allegations of malicious behavior have occurred. (Kind of like a wedding where the priest asks "Is there anyone objecting to this marriage..." and there is an awkward silence) - Waiting for proof of fraud will slow down withdrawals considerably - The main cost of executing transactions on Optimistic rollup comes from putting The cost of sending the data of these transactions to the underlying chain. This data availability problem is common to all rollups, both optimistic and others. In order to prevent funds from being frozen, users must be able to access all transaction data from beginning to end of a rollup. Either the data needs to be sent to layer1, or the user needs additional trust (for example, trusting that the side chain will disclose the data). At the time of this writing, if your rollup does not disclose your transaction data to the chain, then you have to hope that the centralized service provider will not freeze your funds. (Translator's Note: This statement is a bit inexplicable. If an optimistic rollup does not publish transaction data to the chain, then it is not called an optimistic rollup, it is called Plasma.) Data: Ethereum's instantaneous GAS fee dropped to 22Gwei: December 19 News, according to the data website Ultrasound.money, Ethereum’s instantaneous GAS fell to 22Gwei, falling below 30Gwei, which is the recent low point of the Ethereum network. Recently, the gas fee has dropped below 50Gwei many times, which means that the activity of the Ethereum network has been greatly reduced in the near future. [2021/12/19 7:49:20] Advantages: Rich in functions. Can copy the architecture of Eth1.0 and support smart contracts Easier to develop and deploy than zk-rollup Disadvantages: The delay in withdrawing funds is longer. Wait approximately 1 week from when a transaction is made public to when it becomes final. The inconvenience of long withdrawal of funds can be alleviated by underwriters (that is, liquidity providers who charge you a small fee to provide you with L1 funds...) The calculation and state storage are all undertaken by the secondary network. L2 broadcasts the transaction data to the L1 mainnet together with the associated Validity Proof. The so-called "validity proof" is the mathematical proof of the validity of these transactions. A batch of L2 transactions are rolled up into a transaction sent to a smart contract in L1. The prefix "ZK" refers to "zero knowledge proof (zero knowledge)", however, zk rollup often cannot protect privacy - all transactions will be public by default, just like Optimistic rollup. The "zk" prefix is used because the validity proofs these systems rely on are often generated using zero-knowledge proof systems (such as ZK-SNARK or ZK-STARK). The advantage of this scheme is that the storage item update and calculation overhead are removed from the Ethereum main chain, and there is no need to optimistically assume that the broadcasted transaction is correct, as long as it proves to be valid, you will know these The transaction is valid. Immutable X is splitting IMX tokens, and the total amount will increase to 2 billion: On October 22, the NFT second-tier solution Immutable X announced that it will use a ratio of 1:100 before 8:00 on October 23 The total amount of IMX tokens will be split from 20 million to 2 billion. Users who participated in IMX token sales and "Play-to-Earn" activities before will receive the same share of tokens, but the number will increase to 100 times the nominal amount. Immutable X stated that this token split is to improve user experience, because the current value of IMX tokens in a single transaction on the platform is too small. [2021/10/22 20:48:59] This also means that withdrawal times can be much faster than in systems like Optimistic rollup, and require fewer trust assumptions. But the elephant in the room is that zero-knowledge proofs attach a staggering amount of computational overhead to a transaction. Generating a zero-knowledge proof for a computation is about 1 million times more computationally expensive than running the computation directly! This is a rough estimate, and the actual situation may vary greatly due to the characteristics of the original calculation itself, but for the calculation program of the Solidity smart contract type, (this estimate) is generally accurate. The ZK rollup system responds by entrusting the task of constructing proofs to third parties with large computing resources, called "rollup providers". Users rely on these third-party services to create transactions for them. Rollup providers can censor or pre-empt these transactions, just like Ethereum miners can do. The more computing power required, the fewer subjects are capable of acting as suppliers, so we must fully consider the review issue from the protocol architecture. The huge computational overhead also brings some problems to the transplantation of smart contracts. Fully EVM compliant is our goal, so we have to deal with this 1 million times slowdown. EVM is extremely unfriendly to SNARK because its word length is 256 bits, and natively supports SHA3 and other hash algorithms that are unfriendly to SNARK. Even being able to outsource the computational overhead of generating proofs to subjects with large computational resources may not be sufficient. One possible approach is to write the prover algorithm of zkSNARK directly into FPGA hardware or ASIC. The provider then needs this hardware to build proofs. OpenSea delisted the DAO Turtles project on the grounds of illegal financial activities: Jinse Finance reported that on October 11, the NFT trading market OpenSea has suspended the transaction of a DAO Turtles project, claiming that it violated relevant rules for conducting financial activities. An employee of the company wrote that DAO Turtles violated its terms of service, including but not limited to creating, listing or buying securities, commodities, options, real estate or debt instruments\" or through a process including an initial coin offering. A series of methods to raise funds for enterprises or protocols. (theblock) [2021/10/11 20:20:55] The construction of zero-knowledge proofs is much slower than running a normal program. Our Plonk and Pollkup research has put SNARK’s The speed has increased by an order of magnitude, but zk rollup still faces performance bottlenecks compared to optimistic rollup. Generally speaking, the programming languages of SNARK and STARK have to adapt to the inefficiency of the underlying proof system. These languages are implementing variable-length loops and dynamic Memory access (such as dynamic arrays and vectors) will encounter difficulties. Our latest Plookup research has alleviated some problems, but it has not solved all problems. This means that zk rollup requires developers to put their contracts Ported to a custom programming language (such as Starkware's Cairo). For zk rollup that is not fully compatible with EVM, the advantage is that transfers become cheaper. If you do not need to follow the semantics of EVM, you can reduce the broadcast of basic transfers The amount of data. Hermes network does this. The cost of transactions may be cheaper than optimistic rollup, no fraud proof is required, withdrawals are faster than optimistic rollup, and adding functions is slower. Third parties that rely on customized hardware may need higher priority functions customized programming language. Aztec has launched a privacy rollup in March 2021. You can encapsulate your ETH into a privacy shield and use our online privacy wallet zk.money to send private transactions. Privacy rollup uses the same zk rollup is a very similar technology, but with completely different characteristics. The architecture of privacy rollup is to provide strong privacy guarantees for every user of L2. Users hold funds anonymously. When running a transaction, both the sender and the receiver It is anonymous, and the transfer amount is also encrypted. We use the most advanced zero-knowledge proof system Plonk. We invented Plonk in 2019, and it will soon use zero-knowledge proof and develop on the blockchain The team has become the industry standard. Guaranteeing privacy by design requires a rollup architecture that is completely different from zk rollup. We have adopted a privacy-first path because we know that with a public L2, we want to implant programmable Privacy often requires sacrificing user experience or stimulating Progressively refactor the entire protocol. The current Ethereum-based privacy solution is the mixer. The coin mixer can anonymize the user's funds, but otherwise the user is limited.

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