Blockchain and identity security
public key and private key can also ensure the security of new point-to-point transmission in distributed network
in the information transmission of blockchain, the encryption and decryption of the public key and private key of both sides of the information transmission are often not paired.
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.
1. Physical security
the network and host running the blockchain system should be in a protected environment. According to the regulatory requirements of specific business, the protection measures can be used to protect the physical network and host by means of VPN, firewall, physical isolation, etc
2. Data security
in principle, the data exchange between nodes of the blockchain should not be transmitted in clear text. For example, asymmetric encryption can be used to negotiate key, and symmetric encryption algorithm can be used to encrypt and decrypt data. The data provider should also strictly evaluate the sensitivity and security level of the data, decide whether to send the data to the blockchain, whether to desensitize the data, and adopt strict access control measures
3. Application system security
application system security needs to start from the aspects of identity authentication, authority system, transaction rules, anti fraud strategy, etc.
relevant personnel, transaction nodes and transaction data involved in application operation should be controlled in advance and auditable afterwards. Taking financial blockchain as an example, consensus algorithm with stronger fault tolerance, anti fraud and higher performance can be adopted to avoid joint fraud of some nodes
4. Key security
to encrypt the communication data between the blockchain nodes and the key to encrypt the data stored on the blockchain nodes, the plaintext should not exist on the same node, and the private key should be properly saved by the encryption machine. When the key is lost or leaked, the system can identify the relevant records of the original key, such as account control, communication encryption, data storage encryption, etc., and implement response measures to make the original key invalid. The key should also be managed strictly in the life cycle, and should not be permanently valid. It needs to be replaced after reaching a certain time cycle
5. Risk control mechanism
there should be careful detection measures for the network layer, host operation, data access of application system, transaction frequency and other dimensions of the system. For any suspicious operation, alarm, record and verification should be carried out. If illegal operation is found, loss assessment should be carried out, remedial measures should be taken at the technical and business levels, and security measures should be strengthened, And trace the source of illegal operation to prevent further attacks
Article source: white paper on blockchain technology and application development in China
Blockchain technology can help us improve the security of encryption, authentication and other protection mechanisms, which is absolutely good news for the Internet of things security and DDoS Defense Community
blockchain has the potential to become an important solution for safe communities, as well as for the financial, energy and manufacturing instries. At present, verifying bitcoin transaction is one of its main uses, but this technology can also be extended to smart grid system, content delivery network and other application scenarios
how to apply blockchain to network security
whether it's protecting data integrity or using digital identification technology to prevent Internet of things devices from DDoS attacks, blockchain technology can play a key role, at least now it has shown this ability
Internet of things security and DDoS Defense Community
a blockchain startup claims that its decentralized "billing" system can help users resist DDoS attacks with traffic over 100gbps. Interestingly, the company said that this decentralized system allows users to rent their own extra bandwidth and submit their bandwidth access rights to the distributed nodes of the blockchain. When a website suffers from DDoS attacks, the website can use the leased bandwidth to mitigate DDoS attacks
improve confidentiality and data integrity
although the original design of blockchain did not consider the specific access control, now some blockchain technology implementation has solved the problems of data confidentiality and access control. In this era, any data may be tampered, which is obviously a serious problem, but the complete data encryption maliciously guarantees that the data will not be accessed or tampered by others through man in the middle attack in the transmission process
the whole IOT instry needs data integrity protection. For example, IBM's Watson IOT platform allows users to manage IOT data in a private blockchain network, which has been integrated into their big blue cloud service. In addition, Ericsson's blockchain data integrity service provides comprehensive audit, compatible and reliable data services to allow developers to use predix PAAS platform for technical implementation
one of the best applications is the transformation of our public sector and the creation of citizen centered infrastructure. This will enable the public to have their own identity and every transaction can be verified. We can use smart contracts and signed assertions to formulate elements of public services, such as benefits, etc
Internet of things & amp; Smart devices
now the attention of the whole IT community has begun to shift to the Internet of things & amp; Smart devices are on the rise, and security is absolutely one of the primary considerations. Although the Internet of things can improve our work and proction efficiency, it also means that we need to face more security risks. As a result, many companies seek to apply blockchain to protect IOT and instrial IOT (iiot) devices because blockchain technology can enhance authentication, improve data traceability and mobility, and assist record management
according to Alexey malanov, an anti-virus expert at Kaspersky laboratory, blockchain technology helps to track hacker attacks, adding:
"network intruders usually clear the permission log to hide traces of unauthorized access to devices. But if the logs are distributed in multiple devices (for example, through blockchain Technology), the risk can be reced as much as possible. "
German Klimenko, chairman of the digital economy development fund, said: "at present, the Ministry of defense is vigorously promoting it development and research, which is a good thing for the instry."
NATO and the Pentagon are also studying the "defensive" Application of blockchain. This technology is actively used to protect the system from network attacks. NATO will use blockchains to protect financial information, supply and logistics chains, while the Pentagon is developing a data transmission system to prevent hackers
in general, blockchain technology is not omnipotent, at least not yet. Whether from the perspective of technical integrity or system implementation, the current blockchain technology can not guarantee the security of the device 100%. Note: the above content comes from the Internet
this problem is actually very simple
your graphics card is OK! But the vertical synchronization of the graphics card is not off, so the FPS is very low. You can turn off the vertical synchronization in the properties of the graphics card
it must be this problem
the properties of the graphics card can be found by right clicking on the desktop, and then properties - Settings - Advanced<
vertical synchronization is off
in the 3D settings of the graphics card
the leaves are normal
Osmanthus fragrans are cymes clustered in leaf axils, or close to broom shaped, with many flowers in each axil; Bracts broadly ovate, thick, 2-4 mm long, mucronate, glabrous; Pedicel slender, 4-10 mm long, glabrous; The flowers are very fragrant; Calyx ca. 1 mm, lobes slightly irregular; Corolla yellow white, light yellow, yellow or orange red, 3-4 mm long, corolla tube only 0.5-1 mm long; Stamens inserted in the middle of corolla tube, filaments very short, about 0.5 mm long, anthers about 1 mm long, connectives slightly extended at the apex of anthers, showing inconspicuous small tip; Pistil ca. 1.5 mm, style ca. 0.5 mm. Fruit skew, oval, 1-1.5 cm long, purple black. The flowering period is from September to early October, and the fruiting period is in March of the next year.
but the Internet has never been static, and continuous evolution is the norm. In the future, people will have new trust dependence. Because the records of the blockchain can not be tampered with and are authentic, people's trust in the blockchain graally exceeds that of the centralized company. With the joint efforts of many blockchain enterprises and some traditional instries, the world will graally transition from a centralized trust driven to a system driven by algorithms and data. When the centralized trust intermediary is graally weakened, the system represented by blockchain will graally take over the operation mode of the whole world, and finally form the "disintermediated" system trust
therefore, blockchain is not only a technology, but also a story about the paradigm shift of world operation. Although the story is still a little far away, it has sprouted and initially developed
blockchain Internet will start from the instries most closely related to trust and traceability, and graally expand and expand until most instries are blockchain oriented and blockchain +
Puyin is a high-quality Tibetan tea asset, which is stored, identified, evaluated and authorized by three parties. It is a standard digital currency issued through encryption and digitization. Puyin implements the concept of "white paper on standard digital currency" in strict accordance with its operation guidelines, and sets a standard for asset digitization