TLDR：
Due to the lack of unified standards, different blockchains have different architectures and consensus mechanisms, making cross-chain asset transfers complex and costly. Existing third-party bridges face trust and security challenges, and centralized bridges need to maintain liquidity and pass on costs to users. One-click chain launch is similar to solving the trilemma and is a compromise solution for asset bridging.
The market maturity is led by OP Stack and Superchain, and Base is a successful example. AggLayer is natively compatible with Ethereum and is more easily accepted, but the aggregation process needs to be safe and reliable. The success of Elastic Chain depends on the development of ZKSync. OP is optimistic in the short term and ZK is optimistic in the long term.
In the context of insufficient industry innovation, DeFi is still the main application scenario of Rollups. At present, DePIN, RWA and large GameFi projects are less likely to appear on Rollups, while SocialFi and NFT markets may appear, but the market heat is still uncertain. The blockchain as a whole presents a Matthew effect. The trend of unlimited issuance of Rollups is worth paying attention to in the long term and the middle and lower levels in the short term.
1. Connecting island chains: cross-chain issues
When transferring assets across chains, each blockchain has a unique architecture, consensus mechanism, state proof, and state transition, and lacks unified standards and interoperability, resulting in complex cross-chain communication and data exchange. These verification processes are often too expensive to be performed on-chain. This limitation has led to a surge in multi-party signature committees to verify the status of other chains. As a result, there is no universal decentralized standard or protocol that can achieve interoperability between all blockchains, limiting the free flow of assets between different blockchains.
In order to achieve cross-chain asset transfer, many third-party bridges have emerged, but these bridges face significant network security challenges related to trust issues. Even if centralized bridges can ensure complete security, they still need to maintain sufficient liquidity on each integrated chain, thereby passing these operating costs on to users. Currently, the inability to meet the trust difficulty of native decentralized asset bridging and third-party bridges has led ZKsync, Polygon, and Optimism to launch more native solutions such as Elastic Chain, AggLayer, and Superchain Explainer to achieve localized multi-chain expansion.
2、ZKsync 3.0：Elastic Chain
In 2023, Matter Labs, the main development company behind ZKsync, released ZK Stack, a toolkit that allows developers to build their own blockchains based on ZKsync technology. Essentially, these custom chains will be interconnected through Elastic Chain, transforming ZKsync 3.0 from a single Ethereum L2 to Elastic Chain.
The ZKsync 3.0 protocol core upgrade was released on June 7, 2024 and is the most complex upgrade of ZKsync to date. It reconfigures the ZKsync L1 bridge as a shared router contract to support the growing network of interoperable ZK chains. The ZK Stack framework enables native, trustless, low-cost interoperability between chains.
Matter Labs said, “Elastic Chain is an infinitely scalable network of ZK Chains (rollups, validiums, and volitions), which is secured by mathematical verification methods and enables seamless interoperability under a unified and intuitive user experience. It aims to make interoperability within the ZKsync ecosystem smoother and more efficient.”
2.1 Elastic Chain Design
Elastic Chain does not rely entirely on ZK technology, nor can it simply add ZK proof "patches" to other non-ZK multi-chain systems. In general, its network is implemented through three components: ZK Router, ZK Gateway, and ZK Chains.
ZK Router: This is the main routing component of the ZKSync 3.0 architecture, responsible for managing and coordinating communication and data transmission between different chains and nodes in the network, and using efficient cross-chain communication protocols to ensure fast and secure data transmission between different chains.
ZK Gateway: As the entry and exit node of the ZKSync 3.0 network, it handles the interaction between external blockchains (such as the Ethereum mainnet) and the ZKSync network. It is responsible for bridging and transferring assets between external blockchains and the ZKSync network, ensuring the safe and efficient flow of assets between different chains, and realizing comprehensive interoperability between ZK Chains through middleware.
ZK Chains: Ensure the validity and security of transactions by generating and verifying zero-knowledge proofs, and submit the results to ZK Router for Rollup and coordination. They are interconnected with L1 smart contracts through ZK Gateway, are completely independent, customizable, and built using ZK Stack.
According to ZKsync, Gateway is a key component of Elastic Chain, which enables seamless settlement from ZK Chains to Ethereum. Submitting proofs and data to Ethereum through Gateway can achieve the following advantages:
Cross-batch and cross-chain proof synthesis: reducing L1 verification costs.
State delta compression: compresses small batches of data sent to the gateway and efficiently forwards them in larger batches to L1.
Faster finality: Verify chain proofs and prevent conflicts with low-latency cross-chain bridging, enhanced by a large number of validators’ stakes. ZK chains do not need to trust other chains.
Liveness: The liveness of each ZK chain is managed independently by its validators; the gateway does not affect its liveness. Chains can leave the gateway freely.
Censorship resistance: Cross-chain mandatory transactions will be cheaper than regular L1 censorship-resistant transactions, making them more accessible to all users.
ZK Chains do not need to use the ZK Gateway and can settle directly to Ethereum, freely choosing to leave the ZK Gateway network without affecting the security of their chain. They can switch between using the ZK Gateway and settling directly to Ethereum. The ZK Gateway will be operated by a decentralized, trustless cluster of validators to ensure network resilience and reliability. ERC20 tokens are required to participate in this decentralized validation process. The ZKSync network governance will designate a token for this purpose (probably the ZK token).
Validators will receive a bridge fee and a fee for each byte of state delta data published to the ZK Gateway. This incentivizes validators to join the ZK Gateway because their income can increase exponentially with the value of on-chain transactions. In addition, due to the recompression service provided by validators, settling data through the ZK Gateway will be cheaper than settling directly on the Ethereum network, which may be the reason why most ZK chains may choose to join.
3、Polygon 2.0：AggLayer
3.1 Origin of AggLayer Design
Similar to OP Stack and ZK Stack, blockchains created using Polygon CDK can be directly integrated into AggLayer, leveraging its unified bridging and security services to achieve interoperability with other blockchains. This constitutes the core architecture of Polygon 2.0.
The core idea of AggLayer is derived from the Shared Validity Sequencing design proposed by Umbra Research. The design aims to achieve atomic cross-chain interoperability between multiple Optimistic Rollups. By using a shared sorter, the system can uniformly handle transaction ordering and state root publishing of multiple Rollups, ensuring atomicity and conditional execution.
To achieve this, three elements are needed:
Shared sorter: receives and processes cross-chain transaction requests.
Block construction algorithm: The shared sorter is responsible for building blocks containing cross-chain operations and ensuring their atomicity.
Shared Fraud Proofs: Implement a shared fraud proof mechanism between related Rollups to perform cross-chain operations.
Since existing Rollups already have the ability to pass messages between Layer 1 and Layer 2 in both directions, Umbra simply adds a MintBurnSystemContract (Burn and Mint) to complement these three components.
work process:
Burn operation on chain A: can be called by any contract or external account, and recorded in burnTree if successful.
Mint operation on chain B: After being successfully executed by the sequencer, it is recorded in mintTree.
Invariants and consistency:
Merkle Roots consistency: The Merkle Roots of the burnTree on chain A and the mintTree on chain B must be exactly the same to ensure the consistency and atomicity of cross-chain operations.
System Operation:
The shared sorter is responsible for publishing transaction batches and declared state roots for both Rollups to Ethereum. It can be centralized or decentralized (such as Metis). The sorter receives transactions and builds blocks for Rollup A and B. If the transaction on A successfully interacts with MintBurnSystemContract, it attempts to execute the corresponding Mint transaction on B. If the Mint transaction succeeds, it includes both the Burn transaction on A and the Mint transaction on B; if it fails, it excludes both transactions.
3.2 AggLayer Core Components
AggLayer Router: Mainly used to manage and coordinate cross-chain transactions between different blockchains. It acts like a router for cross-chain transactions, ensuring that data transmission and transactions between different blockchains can be carried out quickly and securely. Router uses an efficient cross-chain communication protocol to ensure that data transmission between different blockchains can be carried out seamlessly.
AggLayer Gateway: As a bridge for cross-chain transactions, it realizes the bridging and transfer of assets between different blockchains. Gateway achieves full interoperability between different blockchains through middleware, ensuring that assets can flow safely and efficiently between different blockchains. Gateway can also be used as a tool for asset management and liquidity management, helping users manage their assets between different blockchains.
AggLayer Chains: Unlike other Rollup systems, AggLayer's blockchain ensures the validity and security of transactions by generating and verifying shared validity proofs. These blockchains are interconnected with L1 smart contracts through AggLayer Gateway for seamless interoperability. AggLayer Chains are independent blockchains that can operate independently but interoperate through AggLayer Gateway.
The main goal of AggLayer design is to enable atomic cross-chain operations between multiple blockchains through shared validity sorting and fraud proof mechanisms, thereby providing an efficient and secure cross-chain interoperability solution.
4、Optimism：Superchain
On June 7, 2023, the Optimism Foundation released the Superchain plan, whose goal is to achieve seamless interoperability of various chains through OP Stack, and plans to merge Arbitrum in the future.
Superchain is a decentralized cross-chain network that uses efficient and secure cross-chain communication protocols to achieve data transmission and interaction between different chains.
The core design of Superchain is based on the modular design provided by OP Stack, which allows developers to easily build and deploy their own blockchains and interoperate with other blockchains in Superchain. Each blockchain created based on OP Stack can achieve cross-chain communication and data exchange with other blockchains through Superchain Router and Gateway.
4.1 Superchain Core Components
Superchain Router: Responsible for managing and coordinating cross-chain transactions between different blockchains. It uses an efficient cross-chain communication protocol to ensure that data transmission between different blockchains can be carried out seamlessly. Router can also serve as a router for cross-chain transactions to ensure the smooth progress of cross-chain transactions.
Superchain Gateway: It realizes the bridging and transfer of assets between different blockchains. Gateway realizes the full interoperability between different blockchains through middleware, ensuring that assets can flow safely and efficiently between different blockchains. Gateway can also be used as a tool for asset management and liquidity management, helping users manage their assets between different blockchains.
Superchain Chains: These blockchains ensure the validity and security of transactions by generating and verifying shared validity proofs. They are interconnected with L1 smart contracts through Superchain Gateway for seamless interoperability. Superchain Chains are independent blockchains that can operate independently but interoperate through Superchain Gateway.
Through the modular design of OP Stack, Superchain realizes atomic cross-chain operations between multiple blockchains and provides an efficient and secure cross-chain interoperability solution.
5. Market Outlook
In terms of market selection, Base has been used as a successful case study due to the maturity of OP Stack. AggLayer is closer to Ethereum and may be more widely accepted, but the aggregation process needs to be safe and reliable. The success of Elastic Chain will depend on the development of ZKSync. In the short term, OP has greater potential, while in the long term, the development of ZK technology is optimistic.
6. Current Industry Innovation
In the context of insufficient industry innovation, DeFi remains the main application scenario for Rollups. At present, DePIN, RWA, and large GameFi projects are less likely to appear on Rollups, but SocialFi and NFT markets may see some growth. However, market heat and acceptance remain uncertain. The blockchain industry as a whole presents a Matthew effect, and the trend of unlimited issuance of Rollups is worthy of long-term attention to top projects, and short-term attention to mid- and lower-level projects.
Overall, cross-chain asset transfer and bridging technology are becoming increasingly important in the blockchain industry, but achieving seamless interoperability still faces many technical and trust challenges. Major projects are trying to solve these challenges through different methods and architectural designs to promote the further development of blockchain technology.
