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Daily blockchain knowledge: the difference between public chain and alliance chain (public chain analysis)

Time : 24/08/2021 Author : etw5or Click : + -
        From the release of bitcoin related papers in 2008 to June 2020, the blockchain technology has experienced more than ten years of development, especially in the last five years. From the perspective of media, before 2019, the blockchain circle was mainly "coin circle", and financial institutions' exploration of blockchain was ahead of other industries. However, on October 24, 2019, after the Political Bureau of the Central Committee of the Communist Party of China collectively learned the development and status of blockchain technology, the "chain circle" represented the technology alliance chain and began to gradually enter the public's view. Government affairs, energy More industries such as import and export have begun to pay attention to and explore the far-reaching impact that blockchain may bring in their own fields.
        The blockchain system is a very typical distributed system. Unlike the traditional distributed database, it usually has no master-slave nodes. All participants use point-to-point communication technology, and the default identity is equal. In such an environment, in addition to being affected by cap theory, blockchain technology can not fully take into account the three design goals of decentralization, efficiency and security, that is, the so-called "Impossible Triangle". Both the public chain and the alliance chain conform to this framework, but the design focuses are different. The vast majority of public chains are located in the virtual currency issuance and trading scenarios. They raise funds through telling a story or setting a goal (here mainly refers to legal currency or other more common public chain tokens, such as bitcoin raised by Ethereum before it goes online), and use asymmetric encryption algorithms to generate account addresses and set corresponding account balances. Such behaviors are usually accompanied by huge risks of illegal financing, In May 2017, it was prohibited by laws and regulations of many countries including China.
        Technically, the public chain does not set an access threshold, and anyone can participate. It needs to ensure that as many participants as possible are equal (decentralized), have sufficient security, and can resist attacks by some malicious users. Performance is usually considered as a secondary target. The performance of bitcoin and Ethereum is no more than 30tps (transactionspersecond, transactions / second), while the EOS launched later gains higher transaction performance through the dpos consensus algorithm at the expense of some "decentralization", with a peak of about 4000tps. The biggest difference between the alliance chain and the public chain is that the participants in the alliance chain have clear real identities and certain access conditions. The intentional evil of the participants can usually be directly located.
        In terms of security, the alliance chain is subject to the legal constraints of the real society, which is a natural security baseline. The alliance chain usually serves special business scenarios, such as certificate keeping and traceability. Unlike the number of millions of nodes in the public chain, the number of participants in the alliance chain is usually limited, ranging from tens to hundreds. As the security dimensions of the alliance chain are different, the degree of "decentralization" is also restricted by the business scenario, and different participants have different natural roles in the business. Usually, there are several business data providers and 1-2 supervisors; In terms of performance, the alliance chain design must achieve a high throughput, and cannot drag down the business system. It is generally considered that 4000tps is the most basic requirement.
        The public chain has no restrictions on the participants, and the participants usually participate in the activities on the chain in an anonymous identity. Usually, the corresponding wallet software is downloaded from the participant's own PC. the account address generated by the asymmetric encryption algorithm and the hash algorithm has a certain randomness. It is difficult for any institution to correlate the actual identity of the participant and the wallet address, which also makes the public chain quite difficult to supervise. All kinds of gray transactions and black assets usually use tokens on the chain as payment means, such as blackmail virus. Symmetric encryption algorithm: encryption and decryption use the same string of keys, such as DES, 3DES and AES. It is characterized by high encryption and decryption performance.
        Asymmetric encryption algorithm: the encryption and decryption algorithm does not use a string of keys, usually one is the public key and the other is the private key. The content encrypted by the public key can be decrypted by the corresponding private key; The content encrypted by the private key can be decrypted by the corresponding public key; The public key can be made public, and the private key is controlled by the user. The common use scenario is digital signature and secure key exchange. The algorithm is characterized by low operation performance, which is generally considered to be 1000 times slower than symmetric encryption algorithm. The alliance chain requires the participants to have a clear identity. The identity usually uses a PKI digital certificate, which contains the user's public key and identity information. For the hyperledger fabric of the alliance chain, the participants need to use the CA root certificate bookmark to issue node certificates and user certificates within the organization.
        The development and test environment can use command-line tools such as OpenSSL to self sign the CA root certificate and its corresponding other certificates. In the production environment, it is recommended to use the certificate issued by the authority to realize the real name management of all participants. Different alliance chains and scenarios have different access requirements, which are usually decided by the governance committee composed of the startup members of the entire alliance chain. Multi party voting and setting the voting pass threshold is the admission method of hyperledger fabric, and the certificate issued by the same CA is the technical admission method of bcos. The blockchain consensus algorithm contains two meanings, one is data consensus and the other is business consensus.
        Data consensus refers to the software and hardware algorithms used by nodes to achieve the consistency of the ledger between nodes. Here, it mainly refers to the consistency of the transaction order. Because the transactions, whether in the alliance chain or the public chain, are all with the digital signature of the initiator, which is almost impossible to be tampered with and discarded at most. Business consensus refers to which participants should endorse and guarantee the business meaning represented by the data on the chain to ensure the authenticity of business data. For bitcoin and Ethereum in the public chain, the rules of coin issuance and transfer are their business consensus, while POW is their data consensus. The former stipulates the specific details of the business on the chain, while the latter specifies how data can be agreed between nodes.
        There is a junction between the two. When the pow computing task is completed, a specific number of tokens are generated out of thin air, and the tokens are used to stimulate the provision of data storage and consensus behavior. For the alliance chain, business consensus can be completely separated from data consensus. The authenticity of business data can be generated by one party and endorsed by multiple parties to achieve cross verification. In terms of data consensus, the alliance chain can adopt any consensus algorithm according to the business needs. Because the security design is different from the public chain, the alliance chain can even use Kafka, a non Byzantine fault-tolerant message middleware, to determine the unique order of transactions. Because of this, the alliance chain usually provides more than one consensus algorithm for business participants to choose flexibly.
        Because many kinds of data consensus algorithms can be used, the transaction performance of the alliance chain under specific scenarios can even be comparable to that of the traditional relational database, reaching tens of thousands of transactions per second. Unlike the public chain with a single purpose, the alliance chain can be configured for different scenarios. For example, there is usually no too much correlation between transactions in the deposit type scenario, and it does not care which is the first or the second in the case of large concurrency. It is only simple data verification and sequential writing, so the transaction performance can be very high. If there is correlation between transactions, the transaction sequence has a great impact on the execution result, and it takes more time to determine the transaction sequence and complete the verification logic, then the overall transaction performance will be greatly reduced.
        Most of the transactions in the public chain are transfer type transactions. Transfer from one account to another requires that the balance in the account after transfer cannot be negative. Multiple transactions for a single account in the same block need to be verified and executed in sequence. Take bitcoin as an example. In each transaction, the revenue source of bitcoin under the designated account is the block number generated earlier and the number of transactions in the block, which makes it impossible for bitcoin to perform multiple transfer operations on the same account address in the same block. Ethereum solves this problem by allowing multiple transfer operations on a single account in the same block. However, due to the pow consensus still adopted, The block size cannot be very large, and the transaction performance is still limited, with only dozens of transactions per second.
        In order to improve the throughput of the blockchain, many high-performance schemes have been proposed in the blockchain, such as DAG (directed acyclic graph) and parallel multi chain architecture. The parallel multi chain scheme is relatively easy to understand. Reuse the processing logic of nodes on the chain to create multiple underlying blockchains with the same structure. The difficulty of DAG blockchain is to control the parallel width, represented by iota, byteball and xuperchain. The following figure is a schematic diagram of DAG structure. The governance of the public chain is usually more difficult than that of the alliance chain. Changing the operating parameters of the public chain usually means hard fork (refers to the update of the previous version of the blockchain algorithm) or soft fork (compatible with the previous version of the blockchain algorithm), which is not necessarily in the interests of all current participants.
        The following figure is a code for the public chain to modify the block size, which means that when the block height reaches 115000, the maximum block volume is modified to a larger value. The conclusion of modification can be written in the code, but there are no clear conditions under which it can be modified. Since the public chain cannot specify the specific number of participants, the governance usually needs to be communicated through additional offline forums or offline organizations. The communication cycle is long and the cost is high, and many uncertainties are faced. The governance of the alliance chain is relatively clear. What conditions need to be met for new members to enter, how many participants need to sign to modify the block size, what kind of participants have permission to write in the transaction, and what kind of participants are allowed to query the transaction content. Such governance rules and even permissions can be written in the blockchain as configurations.
        When a specific configuration needs to be modified, any alliance member can initiate a proposal to ask other participants whether they agree. With the passage of time, an alliance chain that cannot meet the business needs needs needs to be adjusted. Rebuilding a blockchain network is often costly, and a strong manageability can bring more powerful business adaptability to the alliance chain. Even if the governance rules are not written into the chain, the alliance chain usually has a clear founder or governance committee because of its limited and controllable members. In this context, governance becomes relatively simple, errors can be traced, and inappropriate parameters can be adjusted in time.
        However, from the macro perspective, the alliance chain still needs more perfect governance system support. Although there are many technical differences between the public chain and the alliance chain, with the integration of the blockchain technology into the "new infrastructure", the technical advantages of the two are constantly merging, and innovation points emerge in endlessly. In the future, there will be more and more blockchain projects with strong performance, high parallelism, rich consensus algorithms, high governance, flexible and easy-to-use contracts. Nowadays, blockchain technology is becoming the driving force for traditional enterprises to complete digital transformation. As an infrastructure for inter enterprise cooperation, blockchain technology will eventually become a trusted channel for enterprise value transfer. Return to Sohu to see more.
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