Any demand-side particihuobi token explorerpant (DSR depositor, Nexus Mutual claimant);
Insured (Insured): Attackers can steal user funds, but they may be unprofitable in doing so. Because they need to provide collateral to participate in the network, and they will be punished for wrongdoing and malicious behavior. If the user's funds are lost, the agreement will compensate the user by confiscation of the attacker's collateral.buy bitcoin australia anonymouslyBonded (Bonded): Similar to the insurance model (for example, the economic benefits of participants are closely related to their behavior), except that the user's collateral is forfeited due to his mistakes and malicious behavior. The type of collateral is important for both the insurance and the mortgage model; endogenous collateral (protocol tokens as collateral) is more risky, because if the bridge fails, the value of the token is also likely to collapse, which further reduces Security guarantee for bridging.
Trusted: Participants do not need to mortgage assets, and users cannot retrieve assets when the system fails or commits malicious behavior. Therefore, security mainly depends on the reputation of the bridge operator."External validators and federalism" are generally better in terms of state and connectivity because they can trigger transactions, store data, and allow data to interact with any number of target chains. However, this comes at the cost of security, because by definition, users rely on the security of the bridge rather than the source or target chain. Although most of the current external validator mechanisms are based on trust models, some require collateralized assets, and a subset of assets is used to insure end users. Unfortunately, their insurance mechanisms are usually reflexive. If the agreement token is used as collateral, it is assumed that the value of the token is sufficient to compensate the user's loss. In addition, if the mortgage asset is different from the insurance asset, it will also depend on the price flow of the oracle, so the security of the bridge will be downgraded to that of the oracle. If a trust model is not required, these bridges are also the least capital efficient, because they promote economic throughput and also need to scale up the scale of collateral."Light client and relay" is also better in terms of state, because the block header relay system can transmit any type of data. Although there are liveness assumptions due to the need for repeaters to transmit information, they are also very safe because they do not require additional trust assumptions. At the same time, they are the most capital efficient bridges because there is no need to lock any assets. However, these advantages come at the expense of connectivity. Every time a pair of chains is connected, the developer must deploy a new light client smart contract on the source chain and the target chain. The complexity of the contract is between O(LogN) and O(N) (the reason is between this The scope is because it is relatively easy to add chain support using the same consensus algorithm). There is also a significant speed flaw in the optimistic model that relies on fraud proofs, which may increase the delay to 4 hours."Liquidity networks" are strong in terms of security and speed because they are locally verified systems (that is, global consensus is not required). They are also more capital efficient than the external validator mechanism of the mortgage/insurance mechanism, because capital efficiency is related to transaction flow/volume, rather than security. For example, assuming that the transaction flows of the two chains are equal, and given a built-in rebalancing mechanism, the liquidity network can contribute to an arbitrarily large economic throughput.The trade-off lies in the state, because although the call data can be transmitted, its function is limited. For example, they can interact with data across chains, where the receiver has the right to interact based on the provided data (for example, using the signature information from the sender to call a smart contract), but there is no "owner" of the data for the transmission or the transmission belongs to Generalized state data (such as minting representative tokens) is not helpful.
Building a strong cross-chain bridge is a difficult problem in distributed systems. Although there have been many attempts in this field, there are still some problems to be solved:Finality & rollbacks: In a chain with probabilistic finality, how does bridging deal with block reorganization and time thief attacks? For example, if any chain has experienced a state rollback, what will happen to users who send themselves from Polkadot to Ethereum?If there is virtual currency "mining" against communication companies, Internet companies, etc., the competent authority shall revoke the value-added telecommunications business license in accordance with the law and be held accountable; if there is virtual currency "mining" against Internet cafes and other entities, the competent authority shall Suspension of business for rectification and other disposals in accordance with laws and regulations.
Bitmain and Yibang International were investigated in Inner MongoliaAs a major power province, Inner Mongolia has always been a key area for Bitcoin mining companies and miners; especially in winter, when hydropower resources in the South shrink, mining companies and miners ship a large number of machines to Inner Mongolia.The Inner Mongolian authorities have always maintained a high pressure on virtual currency mining. However, mining companies and miners have played a "cat and mouse game" with the authorities.As early as November 2019, the Inner Mongolia Department of Industry and Information Technology issued the "Inner Mongolia Autonomous Region Department of Industry and Information Technology Development and Reform Commission, Public Security Department, Local Financial Supervision Administration, and Big Data Development Administration." "Notice" (Nei Gongxin Xin Ruan Zi  No. 384) (hereinafter referred to as "Notice").
The "Notice" pointed out that the Inner Mongolia Autonomous Region's joint inspection team went to some alliance cities to conduct joint inspections on the clean-up and rectification of virtual currency "mining" enterprises. The main contents of the inspection include analyzing the materials reported by the leagues and cities, based on the relevant data held by the autonomous region, focusing on finding out that it has nothing to do with the real economy, evading supervision, and high energy consumption, and enjoying local electricity prices with the "big data industry" as the package Virtual currency "mining" enterprises with preferential policies in terms of, land and taxation.According to China Times, in August 2020, relevant departments of Inner Mongolia conducted an on-site inspection of more than 30 big data and cloud computing companies and found that 21 of them were actually virtual currency mines, so they issued a notice of suspension of work. It is reported that this includes two subsidiaries of Bitmain and a subsidiary of Yibang International.
Relevant personnel of Bitmain responded to the reporter of "Blockchain Daily" today, stating that Inner Mongolia is an important town in the virtual currency mining industry. At that time, Bitmain did set up a mine in Inner Mongolia, but the specific reasons for the investigation and punishment need to be further understood.Yibang International told reporters that their mines in Inner Mongolia used to focus on production testing, and they withdrew after the Inner Mongolia policy became stricter.Chen Xiaohua, a think tank expert on Whale Platform and a review expert on major industrial Internet blockchain projects of the Ministry of Industry and Information Technology, told the reporter of the "Blockchain Daily" that although a new round of rectification has been initiated across the country since May, there are still virtual currencies in some areas "Mining" companies use the "big data industry" as a package to enjoy preferential policies on electricity, land, and taxes, and evade supervision.Chen Xiaohua further pointed out that various localities should not take the daily management of virtual currency mining and transactions lightly. They should use scientific and technological means to conduct routine supervision like Inner Mongolia, focusing on pre-prevention, mid-event control, and post-event disposal.
Kusama has opened the 8th slot auction, which also means that Kusama's relay chain will have an 8th parachain sharing security.The structure of Kusama's relay chain is the same as Polkadot's relay chain. Because of the shared security design, different heterogeneous chains can complete message communication. Facing the difference of heterogeneous chains, Polkadot's cross-chain protocol needs to have some different communication methods.XCM is the message format for communication between different parachains. According to GavinWood's introduction to XCM, we extract part of the introduction to understand XCM.XCM is a message format. It is not a messaging protocol. It cannot be used to actually "send" any message between systems, its role is only to express what the receiver should do.
Polkadot comes with three different systems for actually communicating XCM messages between its constituent chains: UMP, DMP, and XCMP.UMP (Upward Message Passing) allows parachains to send messages to their relay chains.
DMP (Downward Message Passing) allows the relay chain to pass messages down to its parachain.XCMP allows messages to be sent between parachains.
XCM can be used to express the meaning of messages through any one of these three communication channels.In addition to sending messages between chains, XCM is also useful in other contexts. For example, because XCM is abstract and universal, it can be used as a means for wallets to provide a durable transaction format for creating many common transactions. For chains with little business logic changes (such as Bitcoin), the transaction format or the format used by the wallet to send instructions to the chain will generally remain the same.XCM aims to be a language for the exchange of ideas between consensus systems. It should be generic enough to remain correct and useful throughout the evolving ecosystem. It is extensible, and extensibility means changeable, and it also means forward compatibility. It can run efficiently on the chain and can run in a metering environment.XCM can be used in a variety of systems, including gas metering smart contract platforms and community parachains, and trusted interactions between system parachains and their relay chains.Although the goal of XCM is universal, flexible and future-oriented, it must of course meet actual needs, especially the transfer of tokens between chains. Throughout the DeFi world, optional fee payment is very common. You can use the XCM language to perform some specific operations.Importantly, there are many token transfer models that we hope to support: it may only be necessary to simply control the account on the remote chain, allowing the local chain to have an address on the remote chain to receive funds and ultimately transfer the funds under its control to that remote In other accounts on the chain.
But there may be two consensus systems in this process, both of which are specific token systems. For example, tokens such as USDT or USDC have instances on several different chains and are completely interchangeable. It should be possible to destroy such tokens on one chain and mint corresponding tokens on another supported chain. In XCM, it can be called teleport, because the transfer of assets is actually achieved by destroying it on one side and creating a clone on the other side.The core of the XCM format is XCVM. This stands for cross-consensus virtual machine. This is an ultra-high-level non-Turing complete computer whose instructions are designed to be roughly at the same level as transactions.
The "message" in XCM is actually just a program running on XCVM. It is one or more XCM commands. The program will continue to execute, and will not end and stop until it runs to the end or encounters an error.The position in XCM is hierarchical, and some parts of the consensus are completely encapsulated into separate parts. For example, the Parachain of Polkadot completely exists in the internal position of the entire Polkadot consensus. As long as there is any change in one consensus system, it means a change in another consensus system, and the former system is the internal system of the latter.
When working in XCM, it is usually necessary to quote some kind of asset. This is because almost all existing public blockchains rely on some native digital assets to provide the backbone for their internal economic and security mechanisms. For proof-of-work blockchains such as Bitcoin, native assets (BTC) are used to reward miners who develop the blockchain and prevent double spending. For proof-of-stake blockchains such as Polkadot, native assets (DOT) are used as a form of collateral, and network administrators (called equity holders) must take risks to generate valid blocks and obtain physical rewards.Expense payment in XCM is a very important use case. Most parachains in the Polkadot community will require their interlocutors to pay for any operations they wish to perform to avoid "spam" and DDOS.
When chains have good reasons to believe that their interlocutors are trustworthy, they can also not pay. For example, this is the case when the Polkadot relay chain communicates with the Polkadot Statemint public interest chain. However, in general, fees are a good way to ensure that XCM messages and their transmission protocols will not be overused.Let's take a look at how to pay when XCM messages arrive at Polkadot.For systems that do need to pay a certain fee, XCM provides the ability to use assets to purchase execution resources. In a nutshell, this includes three parts:Provide some assets
Exchange assets in terms of computing time (weight in Substrate).XCM follows the instructions
After years of research and development, we finally formed a multi-chain market structure. There are currently more than 100 active public blockchains, many of which have their own unique applications, users, geographic distribution, security models, and design trade-offs. Regardless of what individual communities believe, the reality is that the universe tends to increase entropy, and the number of these networks is likely to continue to increase in the future.This type of market structure makes it necessary for us to obtain interoperability between different networks. Many developers have realized this, and the number of blockchain bridges surged last year, aiming to bring together increasingly fragmented networks. As of this writing, there have been more than 40 different bridging projects.
Interoperability unlocks innovation possibilitiesWith the development of a single ecosystem, they will develop their own unique advantages: stronger security, greater throughput, cheaper transaction fees, better privacy, specific resource supply (such as storage, computing, bandwidth), and Regional developer and user communities, etc. Bridges are important because they allow users to access new platforms and protocols; enable interoperability between protocols; allow developers to collaborate to build new products, and so on. More specifically, they have the following benefits:
Improve the productivity and utility of existing crypto assetsBridging allows existing encrypted assets to be transferred to a new platform to do new things. like:Send DAI to Terra to buy synthetic assets on Mirror, or earn revenue on AnchorSend TopShot from Flow to Ethereum as collateral for NFTfi
Use DOT and ATOM as collateral to lend DAI on MakerExpand the product features of existing agreements
Bridging expands the design space that the protocol can implement. E.g:Use Yearn vaults for liquid mining on Solana and Avalanche
NFT cross-chain sharing order book on Ethereum and Flow on Rarible ProtocolIndex Coop's proof of equity index