Can blockchain secret key be cracked

1. blockchain itself solves the problem of large-scale cooperation between strangers, that is, strangers can cooperate with each other without mutual trust. So how to ensure the trust between strangers to achieve mutual consensus mechanism? The centralized system uses trusted third-party endorsements, such as banks. In the eyes of the common people, banks are reliable and trustworthy institutions. The common people can trust banks to solve real disputes. But how does a decentralized blockchain guarantee trust
in fact, blockchain uses the basic principles of modern cryptography to ensure its security mechanism. The knowledge system involved in the field of cryptography and security is very complicated. Here, I only introce the basic knowledge of cryptography related to blockchain, including hash algorithm, encryption algorithm, information digest and digital signature, zero knowledge proof, quantum cryptography, etc. Through this lesson, you can learn how to ensure the confidentiality, integrity, authentication and non repudiation of the blockchain using cryptography technology
basic course lesson 7 basic knowledge of blockchain security
1. Hash algorithm (hash algorithm)
hash function (hash), also known as hash function. Hash function: hash (original information) = summary information. Hash function can map any length of binary plaintext string to a shorter (generally fixed length) binary string (hash value)
a good hash algorithm has the following four characteristics:
1. One to one correspondence: the same plaintext input and hash algorithm can always get the same summary information output
2. Input sensitivity: even if the plaintext input changes slightly, the newly generated summary information will change greatly, which is greatly different from the original output
3. Easy to verify: plaintext input and hash algorithm are public, anyone can calculate by themselves, and whether the output hash value is correct
4. Irreversibility: if there is only the output hash value, the hash algorithm can never dece the plaintext
5. Conflict avoidance: it is difficult to find two plaintexts with different contents, but their hash values are the same (collision)
for example:
hash (Zhang San lent Li Si 100000 yuan for 6 months) = 123456789012
such a record as 123456789012 is recorded in the account book
it can be seen that hash function has four functions:
simplify information
it is easy to understand, and the information after hashing becomes shorter
identification information
you can use 123456789012 to identify the original information, and summary information is also called the ID of the original information
hidden information
the account book is a record like 123456789012, and the original information is hidden
verification information
if Li Si cheated that Zhang San only lent Li Si 50000 when repaying, both parties can verify the original information with the hash value of 123456789012 recorded before
hash (Zhang San lent Li Si 50000 for 6 months) = 987654321098
987654321098 is completely different from 123456789012, which proves that Li Si lied, Then the information can't be tampered
common hash algorithms include MD4, MD5 and Sha series algorithms, and Sha series algorithms are basically used in mainstream fields. Sha (secure hash algorithm) is not an algorithm, but a group of hash algorithms. At first, it was SHA-1 series, and now the mainstream applications are sha-224, SHA-256, sha-384 and sha-512 algorithms (commonly known as SHA-2). Recently, Sha-3 related algorithms have been proposed, such as keccak-256 used by Ethereum
MD5 is a very classic hash algorithm, but unfortunately, both it and SHA-1 algorithm have been cracked. It is considered by the instry that its security is not enough to be used in business scenarios. Generally, sha2-256 or more secure algorithm is recommended
hash algorithm is widely used in blockchain. For example, in blocks, the latter block will contain the hash value of the previous block, and the content of the later block + the hash value of the previous block will jointly calculate the hash value of the later block, which ensures the continuity and non tamperability of the chain< Encryption and decryption algorithm is the core technology of cryptography, which can be divided into two basic types: symmetric encryption algorithm and asymmetric encryption algorithm. According to whether the key used in the encryption and decryption process is the same or not, the two modes are suitable for different needs, just forming a complementary relationship, and sometimes can be combined to form a hybrid encryption mechanism
symmetric cryptography (also known as common key cryptography) has the advantages of high computational efficiency and high encryption strength; Its disadvantage is that it needs to share the key in advance, which is easy to leak and lose the key. The common algorithms are des, 3DES, AES and so on
asymmetric cryptography (also known as public key cryptography) is different from the encryption and decryption key, and its advantage is that it does not need to share the key in advance; Its disadvantage is that it has low computational efficiency and can only encrypt short content. Common algorithms include RSA, SM2, ElGamal and elliptic curve series. Symmetric encryption algorithm is suitable for the encryption and decryption process of a large number of data; It can't be used in signature scenario: and it often needs to distribute the key in advance. Asymmetric encryption algorithm is generally suitable for signature scenario or key agreement, but it is not suitable for large amount of data encryption and decryption< Third, information digest and digital signature
as the name suggests, information digest is to hash the information content to obtain a unique digest value to replace the original and complete information content. Information digest is the most important use of hash algorithm. Using the anti-collision feature of hash function, information digest can solve the problem that the content has not been tampered
digital signature is similar to signing on paper contract to confirm contract content and prove identity. Digital signature is based on asymmetric encryption, which can be used to prove the integrity of a digital content and confirm the source (or non repudiation)
we have two requirements for digital signature to make it consistent with our expectation for handwritten signature. First, only you can make your own signature, but anyone who sees it can verify its validity; Second, we want the signature to be only related to a specific file and not support other files. These can be achieved by our asymmetric encryption algorithm above
in practice, we usually sign the hash value of information instead of the information itself, which is determined by the efficiency of asymmetric encryption algorithm. Corresponding to the blockchain, it is to sign the hash pointer. In this way, the front is the whole structure, not just the hash pointer itself< Zero knowledge proof means that the verifier can make the verifier believe that a certain conclusion is correct without providing any additional information to the verifier
zero knowledge proof generally meets three conditions:
1. Completeness: authentic proof can make the verifier successfully verify
2. Soundness: false proof can not make the verifier pass the verification
3. Zero knowledge: if you get proof, you can't get any information other than the proof information from the proof process< With more and more attention paid to the research of quantum computing and quantum communication, quantum cryptography will have a huge impact on the information security of cryptography in the future
the core principle of quantum computing is that qubits can be in multiple coherent superposition states at the same time. Theoretically, a large amount of information can be expressed by a small number of qubits and processed at the same time, which greatly improves the computing speed
in this way, a large number of current encryption algorithms are theoretically unreliable and can be cracked, so the encryption algorithm has to be upgraded, otherwise it will be broken by quantum computing
as we all know, quantum computing is still in the theoretical stage, which is far from large-scale commercial use. However, the new generation of encryption algorithms should consider the possibility of this situation.

2. If you lose the mnemonic words in the digital currency wallet, it is almost equal to the loss of the private key. Mnemonic words are just a form of the private key that is easier to understand. If you lose the private key, it is almost equal to the loss of the digital currency in the wallet. With the current technology, it is impossible to crack it. Therefore, if you forget it, you can only recognize it. Change the wallet and back up the mnemonic words

3.

in 2019, the expenditure scale of China's blockchain market will be close to US $300 million

according to the statistical data of in depth analysis report on business model innovation and investment opportunities of China's blockchain instry , released by foresight Instry Research Institute, as of 2017, the expenditure scale of China's blockchain market is only US $83 million. In 2018, the expenditure scale of China's blockchain market will reach US $160 million. It is predicted that the expenditure scale of China's blockchain market will be close to US $300 million in 2019. At this stage, the overall market scale of blockchain is small, because most blockchain projects in the market are in the trial stage, with little investment. On the other hand, many enterprises have realized the potential of blockchain and plan to increase the budget in the future. Affected by this, China's blockchain market will usher in rapid growth. It is estimated that the market expenditure will reach US $1.95 billion by 2023, and the average annual compound growth rate will be 60.51% from 2019 to 2023

statistics and forecast of China's blockchain market expenditure scale from 2017 to 2023

data source: Analysis on adverse factors of China's blockchain development sorted out by the prospective instry research institute

1. Immature technology. At present, blockchain technology is not mature in system stability, application security, business model, etc., which can not meet the requirements of "high efficiency and low energy", "decentralization" and "security" at the same time. First, performance. The transaction throughput that can be carried out on the blockchain is not high, and the current block capacity is very small, which leads to network congestion, and it is difficult to meet the needs of high-frequency business. Many projects are also starting to optimize, but there is still a certain distance from the transaction throughput of real scenes such as banks and stock exchanges. Second, consensus mechanism. In terms of energy consumption, consensus algorithms such as workload proof consume a lot of energy and cost, which makes blockchain waste a lot of network computing power and pairing power; In terms of types, there are too few types of blockchain consensus mechanisms at present. In the future diversified business scenarios, more abundant consensus mechanisms are necessary to adapt. Third, security. Privacy protection, harmful information on the chain, smart contract vulnerability, consensus mechanism and private key protection, computing power attack, cryptography algorithm security and other issues make the blockchain face a severe situation of platform security and application security. Fourth, the database problem. Different from traditional databases, blockchain applications require a lot of write operations, hash calculation and verification operations. The database system for blockchain is still a difficult point to break through

2. Unclear application scenarios

currently, the blockchain project is still in the exploration stage, and no specific landing scenarios can be found. At present, the more promising fields are finance, sharing economy, Internet of things, public services, etc., but from the perspective of the existing blockchain technology maturity, there are still many problems in the application of blockchain, and there is still a gap from the actual use. First, the immaturity of blockchain technology restricts the implementation of commercial applications. At present, although there are many kinds of blockchain core technologies such as privacy protection algorithm and consensus mechanism, they generally do not have commercial availability. Second, the application mode of blockchain is still in exploration, and the "irreplaceable" advantage of blockchain has not been reflected. Blockchain itself represents a consensus system, so we should build a consensus system in line with the corresponding business scenarios from a higher level, rather than just "business + blockchain". There are many users in China, and the business scenario is complex. Moreover, any commercial proct will involve a very large flow and population. The current blockchain technology can not meet the demand

3, lack of professional talents

blockchain technology is a multi-disciplinary and interdisciplinary technology, which mainly involves operating system, network communication, cryptography, mathematics, finance, proction and so on. However, at present, there are still deficiencies in interdisciplinary and fields in China, and the supply of talents in related fields is seriously insufficient. On the one hand, there is a large gap of R & D technical talents. Blockchain technology research and development mainly focuses on go, JavaScript, C and C + programming languages, and new smart contracts use Haskell, Ocaml, rhoang and other new functional programming languages. In China's talent market, there is a big gap for technical talents with senior R & D experience in relevant languages. On the other hand, there is a lack of bottom design talents. Different from R & D technical talents, blockchain bottom system architecture designers need to master a number of interdisciplinary professional skills, not only to deeply understand the block chain bottom design principle, but also to have the system architecture design experience, but also to master the business logic of specific application scenarios. Although some colleges and universities have launched interdisciplinary ecation and blockchain special skills discipline setting, professional talents are still very scarce

analysis of favorable factors for China's blockchain development. In January 2017, the Ministry of instry and information technology issued the development plan of software and information technology service instry (2016-2020), which proposed that the innovation in blockchain and other fields should reach the international advanced level. In August 2017, the State Council issued the guidance on further expanding and upgrading information consumption and continuously releasing the potential of domestic demand, proposing to carry out the pilot application of new technologies such as blockchain and artificial intelligence. In October 2017, the State Council issued the guidance on actively promoting the innovation and application of supply chain, which proposed to study the use of blockchain, artificial intelligence and other emerging technologies to establish a credit evaluation mechanism based on supply chain

in March 2018, the Ministry of instry and information technology (MIIT) issued the key points for standardization of informatization and software service instry in 2018, proposing to promote the establishment of the national informatization and instrialization Integration Management Standardization Technical Committee, and the national blockchain and Distributed Accounting Technology Standardization Committee. In June 2018, the Ministry of instry and information technology issued the instrial Internet development action plan (2018-2020) to encourage the application and research of emerging cutting-edge technologies such as edge computing, deep learning and blockchain in the instrial Internet

since the blockchain was listed in the 13th five year plan for national informatization for the first time in 2016, the national government has paid more and more attention to the blockchain. 24 provinces and cities or regions, including Beijing, Shanghai, Guangdong, Hebei, Jiangsu, Shandong, Guizhou, Gansu and Hainan, have launched dividend policies to carry out the layout of the blockchain instry chain, Actively explore instry applications based on blockchain

At present, China's blockchain technology continues to innovate, and the blockchain instry graally takes shape, and has begun to be applied in supply chain finance, credit reference, proct traceability, right trading, digital identity, electronic evidence and other fields, which is expected to promote China's economic system to achieve technological change, organizational change and efficiency change, To make important contributions to the construction of a modern economic system. With the continuous influx of entrepreneurs and capital, the number of enterprises is increasing rapidly. The application of blockchain will accelerate the landing, boost the high-quality development of traditional instries, accelerate the instrial transformation and upgrading, use blockchain technology to "rece costs" and "improve efficiency" for the real economy, and boost the standardized development of traditional instries. In addition, blockchain technology is becoming a new business form and a new driving force for economic development. Blockchain technology is promoting a new round of business model reform and becoming an important support for building a social system of integrity

In the past, the circulation of physical banknotes was difficult to trace, but with the application of blockchain technology, the flow of all digital assets will have a "chain" to check. For example, in the financial field, blockchain is expected to solve the pain points and difficulties in the payment field, rece the complexity of transactions, improve the end-to-end speed of transactions, rece the communication cost in the transaction process, and improve the transparency and non tamperability of transaction records. The cost of reconciliation, clearing and settlement among financial institutions, especially cross-border financial institutions, has always been very high, and there are complex manual processes. The application of blockchain technology can help rece the cost of reconciliation and dispute resolution among financial institutions, and significantly improve the processing speed and efficiency of payment business, It also makes small cross-border payments possible. In addition, the application of blockchain will also extend to many fields, such as health care, ecation, charity, social management and so on. The market prospect is very broad