Why can Rollup become the hottest Layer 2 solution at present?
Editor's Note: This article comes fromEthereum enthusiasts (ID: ethfans)Editor's Note: This article comes from
Ethereum enthusiasts (ID: ethfans)
Ethereum enthusiasts (ID: ethfans)
, Author: Rajeev Gopalakrishna, Translator & Proofreader: Min Min & A Jian, reproduced by Odaily with authorization.
Unless you hide in the deep mountains and old forests, it is hard not to know the upsurge caused by Rollup, the second-layer scalable solution of Ethereum.
In September 2020, the gas price of Ethereum broke through a record high, exceeding 477 Gwei. Perhaps this indicates that the day when the gas price will rise to Twei is not far away.
Since the ICO boom in 2017, the Ethereum network has not been so congested, and it can be said that the degree of congestion is even higher now. The block gas limit also hit a record high of 12.5 million. Transaction volumes are at levels that peaked in 2017, and block sizes are at an all-time high.
While this is encouraging news for improving the utility of the Ethereum network (at least by these metrics), one could argue that the current underlying scalability issues greatly limit applications and Seriously affected the user experience. However, this problem is not new. The Ethereum community foresaw this problem years ago and has been exploring a solution ever since.
At present, the research of Eth2.0 mainly focuses on the underlying PoS and sharding mechanism. We will soon see phase 0 go live in the next few months. However, the computational scalability of Eth2.0 (that is, state execution through smart contracts in shards) will not be realized until phase 2, which is currently expected to wait until after 2021.
In computer science, all problems can be solved in another roundabout way. —David Wheeler
The roundabout approach taken by Layer 2 solutions is to process transactions on Layer 2 and only use Layer 1 when necessary. Such solutions include state channels, sidechains, and Plasma, among others. Numerous projects have explored these options over the years, and great progress has been made.
More recently, USDT, issued by Bitfinex’s sister company Tether, is currently the largest stablecoin by market capitalization and has been the largest consumer of Ethereum gas. Tether has switched to OMG Network's More Viable Plasma Layer 2 solution.
Reddit hosted "The Great Reddit Scaling Bake-Off" contest to improve the scalability of its Ethereum-based Community Points program (currently only implemented in two subreddits) sex. Currently, the competition has received 22 proposals for Layer 2 solutions.
So, while Eth 2.0 will go live in phases over the next few years, Layer 2 solutions are expected to provide much-needed scalability both before and after.
In the past few years, the research on Layer 2 solutions has mainly focused on state channels and Plasma projects, but the Rollup solution has been very popular recently and has made great progress.
Therefore, this article will delve into Rollup and summarize it in terms of why, definition, and adoption. We will introduce the concepts of two types of Rollup schemes—ZK Rollup and Optimistic Rollup—and some major implementations. Finally, we will also mention various initiatives on the Status Network that may benefit from a Layer 2 approach, as well as our upcoming projects.
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Why use Rollups?
Some background: Scalability solutions built on Ethereum without any modifications to the underlying Layer 1 protocol are known as Layer 2 solutions. These schemes process transactions without interacting with the Ethereum network, and anchor their security on Ethereum's Layer 1 through smart contracts.
Layer 2 schemes are attractive because multiple similar schemes can run on Ethereum, only for those applications that are Layer 2 aware, without requiring everyone to upgrade the underlying infrastructure (which is a very risky big business. project). Although Layer 2 does not necessarily provide the security and determinism of Layer 1, it can increase throughput, reduce costs, and improve user experience compared to Layer 1. For some applications, Layer 2 is sufficient.
Currently, the most promising Layer 2 solutions are state channels and Plasma.
Plasma was proposed by Vitalik Buterin and Joseph Poon in August 2017. Plasma is a scalability framework that transfers assets to/from child chains via smart contracts on the root chain, where all transaction execution occurs on child chains, and state commitments (via default Kergen) will be published to the root chain, and can be used in fraud proofs when exiting the root chain later. There are several variants of Plasma, including Minimum Viable Plasma, More Viable Plasma, Cash, Debit, and Prime. OMG Network's More Viable Plasma is a recent Plasma project that has achieved market adoption.Chinese translationDisadvantages: The biggest disadvantage of state channels is their liveness assumption. Users or their delegates need to monitor Layer 1 at all times in order to deal with various challenges. Plasma not only inherits this liveness assumption, but also introduces the data availability assumption, that is, users need to trust that the operator will provide all transaction data so that they can be used to verify the correctness of the transaction when needed. Without data availability, in the worst case, large-scale problems could arise when users exit the Plasma chain. Neither state channels nor Plasma support smart contracts, which severely limits applications that require EVM compatibility.
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), Rollup does not need to introduce the above two restrictive assumptions. These two assumptions cause inconvenience in many situations. For most applications, Rollup is more promising than state channels and Plasma.
Next let us introduce the definition of Rollup and why it does not need to introduce restrictive assumptions like state channels and Plasma.
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What are rollups?
Rollup is very similar to Plasma, with only one big difference, which avoids the assumption of data availability, that is, all Layer 2 transactions will be "summarized" into a transaction's call data (call data (calldata) is the Ethereum transaction storage data parameter read-only area), and then packaged into blocks and submitted to Layer 1.
Given that the cost of invoking data is much lower than that of Layer 1storage (contract storage), the Rollup scheme allows anyone to obtain transaction data on Layer 2 from Layer 1 at any time (unlike the Plasma scheme, which is just a Merkle root ), used to verify state transitions. Therefore, once Layer 2 data is submitted, it can be obtained from Layer 1. This feature can remove the requirement of liveness assumption and data availability assumption, which gives Rollup an advantage over state channel and Plasma.
ZK Rollup (ZKR): In ZKR, the operator must generate a zk-SNARK validity proof for each state transition on Layer 2, and submit these validity proofs to the Rollup contract on Layer 1. The Rollup contract verifies that these proofs of state transitions from old Merkle roots to new Merkle roots are valid. Although new components are used, these safeguards are cryptographic in nature.Chinese translationAccording to the in-depth comparative analysis, it can be seen that (
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), ZKR is more suitable for token transfers with a shorter finalization time (about 1 to 20 minutes), but it does not support EVM-compatible smart contracts required for general-purpose applications. In contrast, OR is more suitable for applications that require EVM-compatible smart contracts, but by default, the finalization time is longer (about 1-2 weeks), because it needs to wait for the fraud proof challenge period to end. (However, there are techniques that provide economic security to shorten the finalization time and withdrawal time of OR.)
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There are many teams working on ZKR and OR implementations with different assumptions and features designed for different scenarios.
Status Network
ZKR: zkSync developed by the Matter Labs team has been launched on the Ethereum mainnet. Loopring has launched a centralized exchange and payment service using ZKR. StarkEx from the StarkWare team is a ZKR technology that uses zk-STARKs (rather than zk-SNARKs), so it does not depend on trusted settings, is more scalable, and can resist quantum computing attacks.
OR: At least 9 projects are researching different OR variants (for details, please refer to the comparison table in this article). The biggest differences are support for EVM compatibility and the interoperability requirements of the fraud proof challenge. For example, Celer, Nutberry, and Optimism support EVM-compatible smart contracts and non-interactive fraud proofs.
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One of Status' visions is to be a "window on Ethereum". Although Status Messenger does not directly interact with the Ethereum blockchain, the application integrates a secure cryptographic wallet and a Web3.0 browser. Both of these need to interface with Ethereum and are directly affected by gas price spikes due to the scalability challenges mentioned above.
The Keycard product of Status Network is exploring the construction of a payment network designed to meet the credit card-level scalability and instant certainty that the current Ethereum network does not have.
Additionally, Status Network has many other initiatives such as Kudos rewards, Tribute-to-Talk, and ENS domains. These initiatives are very much in need of lower gas prices for viable deployments and a good user experience.
Peer-to-peer: Currently, all Rollup architectures rely on the operator to aggregate all transactions from clients and create blocks using a traditional client-server architecture. The downside is that it may introduce centralization and censorship, and reduce privacy.
in conclusion
Therefore, we on the Status team are exploring how client-operator interactions on Layer 2 can use our decentralized peer-to-peer protocols such as Waku to provide privacy-preserving routing and censorship resistance. For example, using Waku to route transactions to different operators can protect customers' privacy while providing them with different paths to issue transactions while resisting censorship.
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