With the continuous investment of government departments, financial institutions, technology companies and capital markets, the implementation of blockchain technology in practical applications has been accelerated, and the technical bottleneck that blockchain technology needs to break through has been intensified. The specific performance is shown in the following studies direction:
1. Consensus algorithm and performance
The consensus algorithm is the most critical module in the blockchain system. It is mainly used to ensure the consistency of messages in the distributed system. Its core indicators include scalability, security, and decentralization. Among them, scalability usually refers to the speed of system convergence, and also the speed at which the system reaches consistency or "steady state"; security can effectively prevent the possibility of data forgery, and the system is permanently in the security of the protocol abstract theoretical model Within the boundary; decentralization means that the entire system is decentralized, and the greater the number of participating nodes, the better. How to build a blockchain system with good scalability, high security and sufficient decentralization has always been a problem that the academic community is trying to solve. This is also the "impossible triangle" problem of blockchain systems that people often say.
The commonly used consensus algorithms in the existing mainstream blockchain systems include proof of work POW, proof of equity POS, and Byzantine consensus algorithm BFT. Among them, Bitcoin uses a proof-of-work algorithm based on SHA-256 and the longest chain technology to build a proof-of-work algorithm. The average block time is 10 minutes, and the transaction speed is about 7 to 13 transactions per second, which is compared with the actual transaction system. , The difference is far; in response to the problem of insufficient scalability of Bitcoin, Ethereum improved the Bitcoin consensus algorithm, using the uncle block technology to proxy the longest chain, and at the same time improved the hash algorithm, shortening the block generation time to about 15 seconds. Significantly improve the scalability of the chain. In view of the large amount of calculation and waste of resources in the use of proof-of-work algorithms, researchers have tried to use other novel technologies to improve the scalability of the blockchain system. The most representative consensus algorithm is the consensus algorithm based on equity. POS, this method uses a method similar to the proof of equity to calculate the qualifications of the nodes that have the block. This method can greatly improve the scalability of the chain. This type of chain is represented by EOS. In terms of transaction processing speed, the performance is improved by hundreds of times compared with the chain using the proof-of-work algorithm. In addition, a large number of new algorithms have also been applied to the blockchain system, such as the consensus algorithm based on directed acyclic graph technology, the consensus algorithm based on Byzantine fault tolerance, the consensus algorithm based on the HashGraph graph algorithm, and so on.
2. Security enhancement technology
The blockchain system is a very complex system, and all layers may be subject to the risk of attack. It is necessary to adopt technical measures to ensure data security on the blockchain from various aspects such as ledger data, cryptographic algorithms, network communications, smart contracts, and applications. In terms of ledger data, especially for blockchain systems with relatively centralized block producers, such as Neo, EOS and other public chains, in order to meet the consistency and availability of ledger data, it is necessary to adopt data erasure coding technology, data disaster recovery backup and other technologies Means to ensure data security. In terms of cryptographic algorithms, most of the cryptographic algorithms used in public chain systems have unpredictable vulnerabilities and need to be replaced by security-verified national cryptographic algorithms to ensure the security of the core cryptographic algorithms; in terms of smart contract monitoring, the contract’s code logic, The operating environment and the mechanism of the blockchain system itself need to be considered in the contract design process, such as adopting a secure programming architecture, hiring a professional security team to conduct code audits, etc., to ensure the security of the code logic and business level; At the layer, exchanges and digital currency wallets are the channels through which the blockchain system connects users, and are also the most vulnerable areas of security risks. It is necessary to prevent the code from being tampered with during the operation of the code, personal security data being peeped, and other issues such as the loss of the user’s digital assets. Use the mobile terminal Hardware security features are a good way to encrypt applications. For example, Arm-based TrustZone hardware isolation technology, Intel-based SGX hardware isolation technology, etc., can effectively ensure that applications are executed in a trusted environment.
3. Cross-chain technology
Based on the "Impossible Triangle" problem faced by the blockchain system, people are trying to consider the use of horizontal expansion to increase the scalability of the blockchain system, that is, cross-chain technology. By designing multiple blockchain systems that meet different application scenarios, and then using cross-chain technology to realize the free flow of value between chains, it will bring a greater degree of inter-chain collaboration. The existing cross-chain technologies include: notary mechanism, side chain/relay, and hash lock technology. Among them, the notary mechanism selects a trusted third-party node as the prover to realize the value exchange between multiple blockchain systems, represented by Ripple’s Interledger protocol; side chain/relay technology, using smart contract technology The two public chains are anchored to realize the value exchange between the two public chains. The technology is represented by BTC Relay; the hash locking technology is mainly used to solve the problem of insufficient scalability of the Bitcoin system. Hope to lock the technology to build the Lightning Network infrastructure to provide a scalable micropayment channel network for Bitcoin payments on the chain, which greatly improves the transaction processing capabilities of the Bitcoin network outside the chain.
4. Privacy protection technology
With the popularization of blockchain technology, people have found that although the characteristics of openness and transparency can ensure fairness and justice, it may leak the risk of user privacy. For example, the Bitcoin transaction chain data structure makes it easy to know the direction of the flow of funds. Using big data analysis technology, the effective association between the identity of the trader and the real identity can be achieved, thereby gaining user privacy. Therefore, data privacy protection technology for blockchain systems is also one of the key research areas in the academic world. In terms of data privacy, public chain systems with Dash, Monroe, and Zcash as representatives of different technological paths have emerged. Among them, Dash uses a data obfuscation algorithm to split the transaction into many small transactions, and then uses the master node system to mix coins to achieve the purpose of untraceable transactions. Monroe uses ring signature and obfuscated address technology to achieve the purpose of protecting data privacy. The specific principle is that when a transaction occurs, the system will forge multiple transactions at the same time to effectively hide the data information of the trader, and at the same time use obfuscated address technology to hide the sender's address information. Compared with the Dash public chain system, Monero has stronger privacy protection capabilities. For the above two public chain systems, it is still possible to obtain detailed transaction information through technical means. To this end, the researchers used the zero-knowledge proof algorithm to design the Zcash public chain system. The system designed two types of addresses, one for regular transactions and the other for privacy protection transactions, effectively taking into account both efficiency and privacy.
5. Independent identity management technology
Blockchain makes Self-sovereign Identity possible. It itself can be used as a decentralized public key infrastructure (PKI) to make the public key body more useful and safer. The blockchain can be regarded as a decentralized certificate authority that maps identity maintenance to public keys. Smart contracts can also add complex logic, realize revocation and recovery, and reduce the burden of key management for end users. These technologies push the ownership of identities from centralized services to end-to-end services between individuals, and make the identity itself controllable. This is called autonomous identity. This method disperses data and calculations and pushes them to each individual. It is of low economic value for hackers because it requires a lot of effort to attack many individual identities one by one. In the consortium chain, different nodes need to be assigned different permissions and meet certain supervisability. For this reason, it is necessary to build a safe and efficient identity authentication and permission management mechanism. An authentication mechanism based on biometrics technology, or an efficient authentication scheme that combines biometrics and password technology can be used; an efficient and practical password scheme based on identity/attributes can also be used to achieve fine-grained access to nodes/users Control/authority management.
6. Smart contracts and self-organizing business models
Smart contracts have the advantages of transparency and credibility, automatic execution, and mandatory performance. Once it is deployed on the blockchain, the code and data of the program are open and transparent, cannot be tampered with, and will be executed in accordance with the pre-defined logic to produce the expected results, and the execution of the contract will be recorded . It should be said that blockchain technology and its commercial applications are complementary and mutually reinforcing. Self-organizing commercial applications based on smart contracts will help to enhance the value of blockchain technology and expand the scope and field of application of the encrypted economic model. Although from a technical point of view, a smart contract is just a piece of code, it actually carries a lot of business logic, and even a smart contract represents a business model, with unlimited imagination. Conversely, the realization of the self-organizing business model also requires sophisticated design of smart contracts, as well as supporting related technical arrangements such as performance enhancement, security enhancement, and privacy protection. In other words, this is both the creation of a business model and the design of a technical system. The security of smart contracts is of paramount importance. Due to the openness of the smart contract, its code and content can be obtained through public methods, which to a large extent allows hackers to analyze the contract and attack the weaknesses; once the attack is successful, it will cause significant losses. Therefore, there is an urgent need for a complete smart contract detection technology to detect, locate and eliminate loopholes before the contract is put on the chain. There have been many smart contract detection tools or online detection sites, but these detections are still based on experience and cannot do anything about unknown contract vulnerabilities. Formal verification method is a possible solution. By establishing an appropriate model, it can be accurately judged whether the program can run as expected by the developer. But for the formal verification of smart contracts, it is difficult to find a suitable solution, and further research is needed. In the application of smart contracts, on the one hand, it is necessary to clarify the enforceability of smart contracts from the legal level; on the other hand, because smart contracts have natural certainty, they do not have the flexibility and selectivity of ordinary contracts, so in specific scenarios , An intervention mechanism that allows code to suspend or terminate execution needs to be established.
7. Facing the challenge of quantum computers
The direct threat of quantum computing to blockchain and cryptocurrency is mainly manifested in two aspects: massive computing power attacks and cryptographic systems. Quantum computers with different design concepts can bring about qualitative changes in computing speed. For example, a quantum computer that manipulates 50 microscopic particles can handle specific problems more than the fastest "Shenwei·Light of Taihu Lake". supercomputer. Powerful computing power allows quantum computers to easily crack the elliptic curve encryption algorithm currently used in most blockchain projects, so as to deduce the user's private key from the public key through reverse engineering. The private key is cracked, which means that the encrypted assets we own will face the danger of being stolen at any time. Therefore, it is necessary to study anti-quantum computer encryption algorithms, such as lattice-based encryption mechanisms, and use the "shortest vector problem" in multi-dimensional space to build a cryptographic foundation to effectively resist quantum attacks. 8. Integration with other technologies The cloud computing, big data, artificial intelligence, blockchain technology, etc. often referred to are essentially the embodiment of "algorithm + data", with different focuses. Since the essence is connected, the fusion between them is inevitable. For example, in the scenario of asset securitization, the information of multiple business systems needs to be continuously disclosed, and at the same time large-scale distributed file storage needs to be realized.
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