Finality & rollbacks: In a chain with probabilistic finality, how does bridging deal withbitcoin live trading youtube 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?
In addition, security is a scope, we can roughly divide it into the following categories:bitcoin drop percentageTrust-less: The security of the bridge is bound to the underlying blockchain it bridges. Unless the underlying blockchain is attacked by consensus-level attacks, users' funds will not be lost or stolen. In other words, this is not complete trustlessness, because all the economic, engineering, and cryptographic components of these systems contain trust assumptions (for example, there are no loopholes in the code).
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.Bonded (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.17. Create "Five New Towns" commercial landmarks. Accelerate the construction of comprehensive new city commercial centers in Jiading, Songjiang, Qingpu, Fengxian, and Nanhui, gather high-quality consumption resources, promote consumption integration and innovation, optimize commercial layout, and form a new city commercial system with distinct levels, reasonable layout, complete functions, advanced business formats, and misaligned development . Adhere to characteristic development, tap the advantages of resource endowments, rely on the important transportation hub nodes in the Yangtze River Delta, combine historical blocks, urban ecological landscapes, characteristic cultural tourism resources, etc., to form a characteristic consumption function area that combines business, travel and culture. (The Municipal Commission of Commerce, Lingang New Area Management Committee, and relevant district governments are responsible)
18. Improve the energy level and level of the community life circle. Build clusters of public service facilities with a full range of types and high levels of energy, enhance the richness, convenience and safety of community businesses, and accelerate the development of branded chain convenience stores. Accelerate the establishment of a cross-departmental, cross-regional, and industrial chain operation and control system for major and non-staple foods, and further strengthen the ability of mega-cities to ensure supply. Optimize the planning and layout of the standardized vegetable market, and promote the transformation of the standardized vegetable market into a smart vegetable market. Promote the quality and expansion of the housekeeping service industry, and vigorously cultivate leading enterprises in housekeeping services. Improve the breakfast supply system with chain breakfast outlets as the main body and supplemented by various forms such as special single stores, mobile food trucks, and take-out platform distribution. (The Municipal Commission of Commerce and the relevant district government are responsible)The bidding behavior of the Inner Mongolia Development and Reform Commission is a concrete manifestation of the use of scientific and technological means to further implement the virtual currency supervision policy, and also demonstrates the resolute attitude of the Inner Mongolia authorities.On September 15, the Development and Reform Commission of the Inner Mongolia Autonomous Region announced the "Results of Winning the Bid (Transaction) of the Research Project on the Policy Mechanism for Cleaning up Virtual Currency'Mining'". Inner Mongolia Mengze Engineering Management Service Co., Ltd. won the bid for the project with a bid price of 295,000 yuan.The reporter of "Blockchain Daily" learned that this project is a research project for the Inner Mongolia Autonomous Region to clean up the virtual currency "mining" policy mechanism to continuously analyze and discover the secret virtual currency mining in Inner Mongolia.
In fact, as early as 2019, relevant departments in Inner Mongolia issued a policy to clean up virtual currency mining. In 2020, more than 30 big data and cloud computing companies were inspected on-site and found that 21 were actually encrypted mines. Among them are mining machine manufacturing companies Bitmain and Ebang International.In May of this year, Inner Mongolia took the lead in launching a new round of virtual currency mining and rectification activities in China. On May 25, the Inner Mongolia Development and Reform Commission issued the "Eight Measures for the Inner Mongolia Autonomous Region Development and Reform Commission on Resolutely Cracking Down on and Punishing Virtual Currency "Mining" (Draft for Comment).
The "Eight Measures" impose requirements on the prohibition of virtual currency mining on industrial parks, enterprises, Internet cafes, civil servants, and individuals. The punishments for violators are "unprecedented", including the revocation of licenses, inclusion in the blacklist of untrustworthiness, Transfer to discipline inspection and supervision organs for handling, transfer to judicial organs for handling, etc.Industry insiders said in an interview with a reporter from "Blockchain Daily" that although all parts of the country are rectifying, there are still virtual currency "mining" companies in some areas that use "big data industry" as a package to enjoy electricity, land, tax and other benefits. Policies and avoid supervision, the daily management of virtual currency mining and transactions should not be taken lightly. Scientific and technological means should be used to monitor and supervise, and focus on pre-prevention, mid-event control, and post-event disposal.The bidding behavior of the Inner Mongolia Development and Reform Commission is a concrete manifestation of the use of scientific and technological means to further implement the virtual currency supervision policy, and also demonstrates the resolute attitude of the Inner Mongolian authorities.Technical means to monitor virtual currency mining
On September 8, the official website of the Inner Mongolia Development and Reform Commission issued the "Announcement on Competitive Consultation and Procurement of Research Projects on the Policy Mechanism of "Cleaning up Virtual Currency Mining"."According to the announcement, the main content of the research project has 10 items: (1) The generation and development process of virtual currency; (2) The position and attitude towards virtual currency "mining" and supervision situation at home and abroad; (3) The introduction of big data in our district , The original intention of cloud computing companies and the preferential policies provided; (4) the basic situation of the virtual currency "mining" project in our region (including costs, benefits, labor and electricity, taxation, etc.); (5) the virtual currency "mining" in our region Distribution of the main body of “mining”; (6) Identify virtual currency “mining” projects and big data and cloud computing projects through technical means; (7) Analysis of electricity consumption of mainstream mining machines and servers; (8) Clean up virtual currency “mining” "Relevant basis for behavior; (9) Impact on achieving carbon peak and carbon neutrality and accomplishing dual control goals of energy consumption; (10) Virtual currency "mining" behavior to establish a long-term regulatory mechanism related policy research, etc.The announcement shows that the project budget is within 300,000 yuan, and the bid opening time is 9:30 am on September 15.At 16:39 on September 15, the official website of the Inner Mongolia Development and Reform Commission further disclosed the bid winning result of the project. Inner Mongolia Mengze Engineering Management Service Co., Ltd. won the bid with a bid of 295,000 yuan.
According to the industry and commerce information displayed by Tianyancha, Inner Mongolia Mengze Engineering Management Service Co., Ltd. was established on June 23, 2017 with a registered capital of 5 million yuan. The legal representative is Juhuhu. It is mainly engaged in engineering design planning, bidding agency, Engineering project integration and other engineering project management services, etc. From 2018 to 2020, the company won nine government projects in Sichuan and Inner Mongolia.A reporter from "Blockchain Daily" dialed the phone number left on the company's industrial and commercial information, and the result was an empty number.
Inner Mongolia has been at the forefront of the country's crackdown on virtual currency mining. On May 19 this year, the Inner Mongolia Development and Reform Commission issued a report on virtual currency "mining" companies. The reporter of "Blockchain Daily" called the Inner Mongolia Development and Reform Commission at that time. The other party said that virtual currency mining companies have very high energy consumption. Whether it contributes to local taxation or economic contribution, it is almost non-existent. In the future, Inner Mongolia will be used for virtual currency mining. The supervision of the country will remain high pressure.Subsequently, on May 25th, the Inner Mongolia Development and Reform Commission issued the "most stringent" eight measures to provide sites and power support for virtual currency "mining" companies such as industrial parks, data centers, and self-provided power plants. Those who conceal and fail to report, are not cleared and closed in a timely manner, or are not adequately approved and supervised shall be held accountable and accountable in accordance with relevant laws and regulations and internal party regulations.
For the main body of virtual currency "mining", if there are big data centers, cloud computing companies and other entities participating in the virtual currency "mining" behavior, they will all be cleared and withdrawn, and the blacklist of the entry and failure of the mining personnel and the public office of participating in the mining The personnel shall be transferred to the discipline inspection and supervision organs for handling.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.