Exploring the Future Development of Cross-Chain Services

In recent years, numerous independent public chains and Ethereum Layer 2 solutions have emerged in the blockchain field. Due to differences in security, transaction costs, speed, and ecosystems among various chains, users often need to switch between different chains. Compared to the Ethereum mainnet, Layer 2 and other public chains typically offer lower fees and faster transaction speeds. Therefore, users have to rely on cross-chain bridges to reduce costs or use unique applications on specific chains.

A cross-chain bridge can be likened to a "digital asset transport vehicle". Regardless of the threats it faces, this "vehicle" must possess strong defensive capabilities to ensure the safety of the entire process. Every stage, from design and development to actual operation, must be error-free. However, the current cross-chain solutions on the market have more or less architectural design flaws, code vulnerabilities, or reliance on certain trust assumptions, all of which significantly reduce the security of cross-chain bridges.

As a bridge connecting various public chains, cross-chain bridges solve the problem of liquidity fragmentation between different chains and are a key solution for asset cross-chain transfer. However, user demand for cross-chain technology is not limited to asset transfer; this is actually just one application of cross-chain protocols in the DeFi field. Through cross-chain protocols, two completely different networks gain interoperability, which requires not only the transfer of tokens between independent platforms but also support for cross-chain communication of large files and data packets.

In the Web3.0 multi-chain ecosystem, what users actually need is an application that can seamlessly interact with assets and data across all mainstream public chains. In this process, users hope to avoid frequent switching of wallets and networks.

In the current landscape of "one super and many strong" public chains, what users truly need is a more secure, more versatile, and more user-friendly cross-chain communication protocol.

Main Modes of Cross-Chain Communication

Native Verification Mode

Native verification is achieved by running lightweight clients in the virtual machines of both the source chain and the target chain, utilizing relayers for inter-chain communication. This model does not require operating a separate intermediary chain. If zero-knowledge proof technology is adopted, it can also eliminate trust assumption issues present in certain solutions.

external verification mode

External validation relies on one or more validators monitoring specific addresses on the source chain. When a user sends assets to a designated address on the source chain, the assets are temporarily locked. After third-party validators verify this information and reach a consensus, the corresponding assets are generated on the target chain.

The main drawback of this model is the existence of a "trust assumption," making it vulnerable to asset theft due to "single point of failure" or "local failure."

Local Verification Mode

Local verification is a peer-to-peer liquidity network. Each node acts as a "router", providing native assets on the target chain instead of derivative assets.

The limitation of this model lies in the lack of "universality"; it is only applicable to asset cross-chain transfers and cannot support the inter-chain transmission of general information and data.

upstream chain model

The upstream chain requires applications to deploy smart contracts on its chain in order to replicate and send messages to other Layer 1 public chains for state updates.

The main disadvantage of this model is reflected at the business level, as this chain will compete with all Layer 1 chains rather than cooperate, since they are all vying for applications to be deployed on their own chains.

zkRelayer: The Key to Cross-Chain Communication

An excellent cross-chain communication solution should have the following characteristics:

• Trustless assumption, secure and reliable
• Permissionless, decentralized
• Highly versatile
• Scalable
• Fast, low cost

Not all cross-chain solutions can meet these conditions simultaneously, and the importance of each feature varies. Users may accept relatively slower or more expensive cross-chain services and may not immediately need cross-chain transmission that supports various data formats. However, the characteristic of "trustless assumption" is indeed the most urgent and important.

Early external verification models attempted to solve the communication problems of other public chains with a single chain. From a methodological perspective, this is a rather cumbersome approach, making it difficult to resolve the communication challenges between EVM and non-EVM, as well as PoW and PoS chains. At the same time, the intermediary chain itself is a single centralized tool, making it difficult to "prove its own innocence," lacking both decentralized security and trustless security.

In the native verification mode, certain solutions primarily emphasize the roles of the sender and receiver clients, downplaying the importance of relays and oracles. There are the following issues: first, users must trust that relays and oracles will not collude maliciously; second, users must also believe that the protocol itself will not act maliciously in the relay phase. In other words, it is difficult to achieve true trustless security in existing solutions. Single points of failure and local failures are like a time bomb, lurking in cross-chain communication solutions with inherent flaws.

zkRelayer is an innovative zero-knowledge proof relay for cross-chain communication. Its greatest advantage is that users do not need to trust any external third parties, or even the protocol itself. As long as the mathematical and cryptographic proof process is complete and correct, this system can gain public recognition. It is worth noting that a fundamental change has occurred here: users trust "truth," rather than any individual or organization. Individuals or organizations may make mistakes or act maliciously, but truth never does.

Throughout the communication process (Chain A → Sender → zkRelayer → ZK Verifier → Receiver → Chain B), the position of zkRelayer will surpass that of the two lightweight clients, Sender and Receiver, becoming the core of the entire solution.

The core components of zkRelayer include ZK provers and message aggregators. The zero-knowledge proof method used features characteristics such as fast, recursive, and trustless, achieving the theoretical limits in terms of proving and verification time. Applying this technology to cross-chain communication relays ensures that the entire communication process is trustless, efficient, and low-cost.

zkRelayer is expected to be the key to ushering in a new era of inter-chain communication. With its support, inter-chain communication will enter a brand new stage of development.