What’s the significance of XCMP to Polkadot?

What is the significance of Cross-chain Message Passing (XCMP) to Polkadot and the whole blockchain industry?

In this PolkaWorld Topic Discussion, we organized six Substrate / Polkadot developers to talk about their views on XCMP. What is the simply understand of XCMP？How it works in Polkadot？Let’s see how developers discuss it.

1. Xiliang Chen, CTO of Laminar

A less accurate metaphor:

Bitcoin network is just like a large server, with very perfect (and expensive) security, only one program is allowed, that is, accounting. Limited speed, limited function, but as the only server so ubiquitous and so secure in the world, everyone is willing to use it.

Ethereum has rebuilt a large-scale server with perfect security. But unlike bitcoin, this server can support different applications when developers upload their own software. Different applications can call each other directly and build a rich ecosystem. But as a server, the performance is limited, different applications also need to compete for the right of execution, there are various disadvantages.

So what to do now? If the performance of one server is not enough, build more servers. But it is very expensive and difficult to build a decentralized server. So Polkadot provided a solution: I can built a computer room with 100 servers at the beginning. You can rent one of them to you for a small amount of rent, and I will help you with all the security. This is the sharing security of Polkadot, so that parachain can share the security of Polkadot network cheaply.

But a single server is not enough. For example, to develop a game chain, you need to give users a recharge function. The user’s account book may be placed on another server, so a crosschain protocol is needed to recharge. If the ledger server and the game server are not in the same computer room, then all interactions have to cross the security barrier, which is very difficult. However, the interaction between parachain and relaychain of Polkadot is much simpler, because their servers are in the same computer room, and they can have internal directly connected network cables, so the interaction does not need to cross the security barrier. In this way, projects between Polkadot ecosystems can interact efficiently and safely across chains, this is XCMP.

2. John, Polkadot Technical Ambassador

As we know, Polkadot is composed of relaychain and many parachains (including parathread ). I have always compared the whole architecture of Polkadot to the super upgraded version of Ethereum: in other cases, the smart contract in Ethereum is an application chain in the form of parachains in Polkadot. We all know that the contracts of Ethereum can interact with each other. For example, you can take Dai generated by MakerDao to Uniswap to trade. This is because the call language among all smart contracts in Ethereum is unified, that is, one smart contract can understand the information sent by another smart contract. Since Polkadot is an upgraded version of Ethereum, and the contracts can interact with each other, the application chain must also be able to interact with each other. XCMP specifies the interaction specification between these application chains and relaychain. Application chain can also understand each other’s information through relaychain, so Polkadot is no longer a loose collection of some sporadic blockchain, but a huge ecosystem to maintain interaction. On the basis of the Substrate development framework, it is the XCMP that makes Polkadot become the leader of heterogeneous sharding. In terms of design architecture, Polkadot is worthy of being the next generation of Ethereum.

3. Xiao Zhang, Polkadot Technical Ambassador

From the current development of blockchain technology, the future blockchain network must be coexistence of multiple blockchain structures. Because different application use case have different requirements for blockchain design. For example, some blockchains need to be efficient, some need to protect privacy, some need to support specific hardware, some need to comply in a certain country. So the idea of “designing a blockchain to take care of the world and meet all application use case” is unrealistic and unlikely to be realized. From the perspective of computer engineering, there is no best design, and everything is trade-off.

Since multiple blockchains must coexist in the future, the communication between chains is very important. Otherwise, we will return to the era of information island and data chimney. The biggest design advantage of Polkadot crosschain is that it can realize the interconnection of value and information between chains. To make a simple analogy, you can think of each blockchain as a country. Value exchange is equivalent to building an international financial and trade market so that capital and goods can flow across borders. Information exchange is equivalent to building an international Internet so that information can be shared across borders. In this way, all countries in the world have entered the era of global division of labor and development from a state of isolation and self governance. It is self-evident that this will promote human civilization.

The function and significance of XCMP to Polkadot is equivalent to the TCP / IP protocol in the Internet world. Parachains with different structures and functions are connected through a unified XCMP protocol. Each chain focuses on its own work and then through ingenious arrangement and combination and network amplification effect, it can realize dazzling application innovation. For example, a blockchain design of a data asse we are now demonstrating may use functions related to data storage, storage and authentication, DeFi stablecoin, tokenization and privacy computing. Each function is provided by a corresponding parachain. When combined, a science fiction data asset market blockchain can be realized.

It is worth mentioning that there are not a few blockchains with the slogan of crosschain. However, this crosschain is not the other crosschain. XCMP protocol can be implemented on the Polkadot blockchain, which is inseparable from the excellent design of Polkadot, especially the idea of shared security model and the bridge model.

4. Jianjiang Wang, CTO of Acala Network

In Ethereum, some Dapps that you have thought of and haven’t thought of may have been realized, and these Dapps complement each other and connect with each other. For example, DeFi, as we are familiar with, is a commercial whole composed of many Dapps, such as over collateralized stablecoin, decentralized exchange, and peer-to-peer lending.

Based on the consistent operation environment and interface provided by Ethereum, DAPP can freely transfer information and operate each other. Ethereum ecology seems to be a common life body with continuous divergent needs and self circulation. However, the design of the bottom layer determines the innate inadequacy and extreme fragility of this life body. All Dapps are using the same bottom layer resources. When the pressure is not high, it seems that they operate in an orderly manner. When there is a price collapse or the like, the Ethereum network usually starts to become congested, and some Dapps are almost stagnant, and users suffer huge losses.

We can’t help thinking about how the poor performance of Ethereum itself can meet the needs of decentralized business applications?

First of all, the need to transfer information between Dapps does not mean that all their businesses need to communicate across Dapps, nor that all Dapps need to communicate with each other in two ways. The blockchain industry needs to come up with better solutions to achieve both high-performance and low-cost information transfer.

Polkadot’s XCMP enables DAPP to choose to run on a parachain of independent computing resources, with high TPS to handle business. Information can be transferred between parachains through the hub of relaychain. The whole process is subject to consensus constraints, enjoying independent resources and communicating with each other. The normal competition between Dapps for underlying resources will no longer exist. This system composed of parachains and relaychain is more robust, with more commercial possibilities, which is also an important reason for Acala to choose Polkadot eco. If the past proves that the decentralized business model is feasible in Ethereum, Polkadot is carrying the real star sea of decentralized business and making those come true.

5. Marvin, cofounder of Phala Network

The industry recognized that the difficulty of crosschain is to achieve real interoperability under the premise of maintaining security and performance: the difficulty of this part is to realize crosschain data communication, because there are many solutions available for crosschain assets. So if we can’t make full use of Polkadot’s cross chain ability, it’s meaningless to just be a parachain. When a parachain is connected to Polkadot, it means that it has the communication ability between parachains. XCMP protocol realizes the communication between chains, and the consensus algorithm of Polkadot mainly serves for it.

The parachain can send messages to another chain, and XCMP ensures that the messages are delivered to the destination in order and accurately. The chain of received messages can be interpreted in any logic. Polkadot creatively realizes the “sharing security” between chains, which not only ensures the block generation and acceptance of parachain, but also maintains the consistency of the whole network state. On the network without shared security, any operation needs a lot of block confirmation time (just like centralized exchange). The certainty of the network is the key to the implementation of XCMP. I’ll talk about it from two perspectives:

The first is network effect. At present, there are two ways of crosschain:

• The first is an independent bridge, such as eth-btc bridge, which is generally used to connect two independent chains. A typical example is RSK, which is implemented in the way of alliance. It creates a multi signature wallet on BTC, which is held by multiple institutions. These institutions observe that collection will generate crosschain assets on the RSK chain, and vice versa. If both sides of the bridge support smart contracts, a more decentralized protocol can be implemented.
• The second is the bridge on the Polkadot parachain. What Polkadot provides is actually the communication ability between parachains, but if the chain in Polkadot wants to communicate with the chain outside Polkadot, it needs to use the bridge. One or more bridges can be realized on the parachain, just like the independent bridge just mentioned, various technologies can be adopted. But because Polkadot provides communication between parachains, a bridge realized on a parachain can not only serve itself, but also other parachains. This creates a network effect.

The second is the efficiency improvement based on sharing security.

If you pay attention to Polkadot, you will find that they have been repeatedly mentioning the concept of “shared security”, which is a very important function. It can be said that without shared security, the significance of crosschain will be greatly reduced.

Polkadot allows parachains to call each other. For example, the token sent from my chain can be used by another DEX chain. Everyone has used the exchange, and it needs to wait for several blocks to confirm the withdrawal of money, which is to ensure the safety of transfer. If you don’t wait and the transaction hasn’t settled, the exchange will lose money once the chain rolls back and other problems occur. The design of Polkadot solves this problem. The transaction of all chains is executed synchronously and verified by Polkadot validators.

This security cross chain capability is the main reason for us to choose Polkadot. At present, Polkadot parachain has been open-source and will be launched soon. Detailed XCMP will also be launched soon.

XCMP is a very basic infrastructure. It is still a very heavy work to directly use XCMP to realize the crosschain of application layer, because XCMP is only responsible for sending messages, but does not define how the receiver responds. The solution proposed by Polkadot is called SPREE (Shared Protected Runtime Execution Enclaves): SPREE allows to open a security area independent of the parachain on each parachain, in which the recognized security code is executed to ensure that the code will not be interfered by the parachain, so as to solve the problem of untrustworthy receiver. Using SPREE can realize very efficient crosschain asset transfer. This part is very similar to the idea of TEE, of course, we appreciate it so much.

6. Sota, CEO of Plasm

Polkadot is the foundation for the next innovations. From my understyanding, this means that we can create combined use cases. Let’s say if Plasm Network and Acala Network are connected, we can make scalable, instant and stable coin payment system. This is a simple example. The more blockchains are connected, the more use cases we can make. This is a game changer.

More information about XCMP can be found in this article：https://medium.com/web3foundation/polkadots-messaging-scheme-b1ec560908b7

Polkadot wiki of XCMP：https://wiki.polkadot.network/docs/en/learn-crosschain

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