Ethereum summary
If you want to understand the application of blockchain, you can refer to many books and opinions, such as illustrated blockchain, blockchain: reshaping the economy and the world, blueprint and guide of new economy, and articles of coin'an community, including a detailed understanding of the platform of coin'an community, with great strength
As the name suggests, blockchain is composed of block and chain. It is a new application mode of computer technology such as distributed data storage, point-to-point transmission, consensus mechanism, encryption algorithm and so on. It is a kind of chain data structure that combines data blocks in order according to the time sequence, and it is a secure and reliable distributed account book that can not be tampered with and forged by means of cryptographyin 2008, in his paper bitcoin: a peer-to-peer e-cash system published by Nakamoto, he first proposed the idea of blockchain and encrypted digital currency. Starting from bitcoin, blockchain has become the underlying technology of various digital currencies
Second, the working principle of blockchain:1. The basic concepts include: (1) transaction: one operation will change the account status once, such as adding a record 2) Block: records the transaction and status data within a specified time, which is a consensus and preservation of the current account status 3) Chain: it is composed of a series of blocks in chronological order, which is the log record of the whole state change. If you understand the working concept of blockchain, it is not difficult to understand its working principle. Suppose there is a distributed data logbook, which can only be added, not deleted or changed. Its structure is a linear chain formed by a series of "blocks" (which is also the source of the name of "blockchain"), and new data must be put into a new block to be added, The maintenance node can propose a new block, but it must go through a certain consensus mechanism to reach an agreement on the final selected block
2. Take bitcoin as an example to see the working principle of blockchain
the block of bitcoin is divided into block head and block body
Core advantages and characteristics of blockchain1. The verification, accounting, storage, maintenance and transmission of decentralized blockchain data are all based on distributed system structure. There is no centralized hardware or management organization, and the rights and obligations of any node are equal, The data blocks in the system are jointly maintained by the nodes with maintenance function in the whole system. 2. The open and transparent system is open. In addition to the private information of all parties to the transaction is encrypted, the data of the blockchain is open to all. Anyone can query the blockchain data and develop related applications through the open interface, so the information of the whole system is highly transparent. 3. Security blockchain uses consensus based specifications and Protocols (such as a set of open and transparent algorithms) to enable all nodes in the whole system to exchange data freely and safely in a de trusted environment, so that the trust in "people" is changed into the trust in machines, and any human intervention does not work. 4. Information cannot be tampered with. Once the information is verified and added to the blockchain, it will be stored permanently. Unless more than 51% (almost impossible) nodes in the system can be controlled at the same time, the modification of the database on a single node is invalid. Therefore, the data stability and reliability of the blockchain are extremely high. 5. Anonymity because the exchange between nodes follows a fixed algorithm, and its data interaction does not need trust (the program rules in the blockchain will judge whether the activity is effective or not). Therefore, the counterparties do not need to let the counterparties generate their own trust by disclosing their identities, which is very helpful for credit accumulation
At present, the most popular classification of blockchain is to divide blockchain into public blockchain, private blockchain and consortium blockchain according to different participants1. Public chain: anyone can participate in the use and maintenance, and can obtain the effective confirmation of the blockchain. Public chain is the earliest blockchain and the most widely used blockchain at present, such as bitcoin blockchain. The information is completely public
if the licensing mechanism is introced, it includes private chain and alliance chain. 2. Private chain: a company or indivial only uses the blockchain technology, enjoys the exclusive write permission of the blockchain, and does not disclose the information. At present, conservative giants (traditional finance) want to experiment with private blockchain, and the application procts of private blockchain are still groping. 3. Alliance chain: it is a blockchain between the public chain and the existing chain, which is jointly controlled by multiple organizations. The use of the chain is managed with authority, which can be controlled by the manager, and also open to others according to the manager's wishes. In addition, according to the different use scenarios and purposes of blockchain, it can be divided into currency chain for the purpose of digital currency, property chain for the purpose of recording property rights, and crowdfunding chain for the purpose of crowdfunding
On May 28, Ma Huateng, CEO of Tencent, proposed the anti-counterfeiting method based on cloud integrated blockchain technology, which is far more efficient than traditional anti-counterfeiting methods. The future anti-counterfeiting verification scenario may only require users to use their mobile phones for simple scanning, and a large number of complete information based on different dimensions can be obtainedtake Maotai liquor as an example:
distillery address, proction workshop, operation staff, inspector, delivery time, transportation vehicle information and driver information,
liquor year, raw material source, raw material supplier, storage warehouse number, raw material transportation vehicle and driver information,
all information can be accurately traced, permanently recorded and tampered with
the above information can be easily verified
2. Food safety issues as early as last November, Wal Mart has cooperated with IBM to track the source of food by using blockchain technology, so as to ensure the safety of food and increase the circulation of food to rece costs. For Wal Mart and other large supermarkets, it took a few days to investigate the source of problem food, After using this technology, only one item of proct information is needed to achieve accurate traceability, and important information such as food origin, inspector, supplier, logistics and transportation can quickly find problems in a few minutes. Currently, procts tracked by blockchain include packaging procts from the United States and pork from China
3. Information security
blockchain technology is promoting an information security technology revolution. (1) identity protection PKI is a common public key encryption technology in e-mail, message application, website and other communication applications. However, since the implementation of most PKI, the centralized trusted third party certification authority (CA) is used to issue, activate and store user certificates. Hackers can attack PKI to fake user identity or crack encrypted information
certcoin is the first PKI implementation of blockchain, which comes from MIT, removes the centralized authentication center, and uses blockchain as a distributed ledger for domain name and public key
pomcor company: blockchain PKI implementation path: keep the authentication center, and use blockchain to store the hash value of issued and activated certificates. Users can verify the authenticity of certificates through decentralized and transparent sources, and can also improve the network access performance through local authentication of secret key and signature based on blockchain
(2) data integrity protection
guardtime developed a secret key free signature architecture (Ksi) based on blockchain technology to replace the secret key based data authentication technology. Ksi stores the hash table of the original data and files on the blockchain, runs the hash algorithm to verify other copies, and compares the results with the data stored in the blockchain. Any data tampering will be found quickly because the original hash table is stored in millions of nodes
(3) key infrastructure protection
the "Achilles heel" of the Internet, DDoS has entered the TB era, DDoS is still the simplest weapon for hackers to bring down the big target with low cost, DNS service is the primary target for hackers to carry out large-scale destruction, but blockchain technology is expected to fundamentally solve the problem
The distributed storage ofblockchain makes hacker attacks lose focus. Nebulis is developing a distributed DNS system, which uses Ethereum blockchain and interstellar Internet file system (IPFs, the distributed substitute of HTTP) to register and resolve domain names. The biggest weakness of DNS is caching, which makes DDoS attacks possible. It is also the bane of the centralized government's censorship of social networks and manipulation of DNS registration. A highly transparent and distributed DNS system can effectively prevent any entity, including the government, from arbitrarily manipulating records
(1) digital currency: improve the convenience of currency issuance and use, such as bitcoin and Ethernet in foreign countries, and guorenbao in Chinafrom the use of physical transactions, to physical currency and credit currency, and then to the rise of bitcoin network, more and more people are aware of the distributed ledger blockchain technology behind it, and graally apply it in many scenarios other than digital currency
(2) cross border payment and settlement: realize point-to-point transaction, rece intermediate fees
transfer and payment. At present, the most mature application of blockchain technology is payment and transfer. Blockchain technology can avoid complicated systems, save the process of inter-bank reconciliation and review, and accelerate the settlement speed; virtual currency can rece transaction costs without the intervention of clearing house. Different countries have different clearing proceres. It takes two or three days for a single remittance to arrive, which is inefficient and accounts for a large proportion of funds in transit. No longer through the third party, through the blockchain technology to form point-to-point payment. By eliminating the link of the third-party institutions, we can make full day payment, real-time payment, withdraw cash quickly and rece the hidden cost, which helps to avoid the capital risk. It is timely and convenient
(3) bills and supply chain financial business: rece human intervention, rece costs and operational risksvalue transfer between point-to-point, control and verify physical bills or central system; Intermediaries will be eliminated and human intervention reced. With the improvement of efficiency, financing channels are more unblocked, risks are lower, and multiple parties benefit
(4) securities issuance and Trading: realize quasi real-time asset transfer, accelerate the speed of transaction clearing
the application of blockchain technology can make the process of securities trading more concise, transparent and fast, rece the plication of IT system, and improve the efficiency of market operation. For stocks, blockchain can eliminate paper and pen or electronic form records, rece human errors in trading, and improve the transparency and traceability of trading platform. Citigroup and Nasdaq cooperate to promote blockchain applications
(5) customer credit investigation and anti fraud: rece the cost of legal compliance, prevent financial crimes
the customer information and transaction records recorded in the blockchain help banks identify abnormal transactions and effectively prevent fraud. The technical characteristics of blockchain can change the existing credit reference system, and store the data of customers with bad records in the blockchain when the bank concts "know your customer" (KYC)
equity crowdfunding:
Blockchain blockchain is a new application mode of computer technology such as distributed data storage, point-to-point transmission, consensus mechanism and cryptocurrency algorithm. Is a shared distributed ledger in which transactions are permanently recorded through additional blocks
2, block - block
in the bitcoin network, data will be permanently recorded in the form of files, which we call blocks. A block is a set of records for some or all of the latest bitcoin transactions and is not recorded by other previous blocks
3. Node -- a of the ledger operated by the participants of the blockchain network
Decentralization is a phenomenon or structure, which can only appear or exist in a system with many nodes or in a group with many indivials. The influence between nodes will form nonlinear causality through the network5. Consensus mechanism
consensus mechanism is to complete the verification and confirmation of the transaction in a very short time through the voting of special nodes; For a transaction, if several nodes with unrelated interests can reach a consensus, we can think that the whole network can also reach a consensus
6. POW -- proof of work refers to how much money you get depends on the amount of work you contribute to mining. The better the performance of the computer, the more money you will be given
In POS mode, your "mining" income is directly proportional to your currency age, and has nothing to do with the computing performance of the computer8. Smart contract
smart contract is a kind of computer protocol which aims to spread, verify or execute the contract in an information way. Smart contracts allow trusted transactions without a third party, which are traceable and irreversible
9, time stamp
time stamp refers to the string or encoding information used to identify the recorded time and date. The international standard is ISO 8601
Turing completion refers to the ability of a machine to perform calculations that any other programmable computer can perform DAPP decentralized application is an open source application that runs automatically, stores its data on the blockchain, motivates it in the form of cryptocurrency token, and operates with protocols showing valuable proof Dao, a decentralized autonomous organization, can be regarded as a company that operates without any human intervention and gives all forms of control to a set of unbreakable business rules13. Privatekey - private key
a private key is a string of data that allows you to access a token in a specific wallet. As cryptocurrency, they are hidden except for the owner of the address
14. Publickey -- public key
is paired with private key. The public key can calculate the address of the currency, so it can be used as a certificate to own the address of the currency
15, miner
try to create a block and add it to the computing device or software on the blockchain. In a blockchain network, when a new effective block is created, the system will automatically give the block creator (miner) a certain number of tokens as a reward
16. The mine pool is a fully automatic mining platform, which enables mining machines to contribute their computing power to mine together to create blocks, obtain block rewards, and distribute profits according to the proportion of computing power contribution (that is, mining machines access the mine pool - provide computing power - obtain income)
17, public chain
fully open blockchain, refers to anyone can read, anyone can send transactions and transactions can be effectively confirmed, people all over the world can participate in system maintenance, anyone can read and write data through transactions or mining
18. Private chain
write permission is only for the blockchain of a certain organization or a specific few objects. Read permission can be open to the outside world or restricted to any extent
19, alliance chain
consensus mechanism is a blockchain jointly controlled by several designated institutions
20, side chain
wedged side chains technology, which will realize the transfer of bitcoin and other digital assets between multiple blockchains, which means that users can access the new cryptocurrency system when they use their existing assets
21, cross chain technology
cross chain technology can be understood as a bridge connecting the blockchains, and its main application is to realize atom transaction, asset conversion, information exchange within the blockchain, or solve Oracle problems among the blockchains
22. The hard fork
blockchain has permanent divergence. After the release of the new consensus rules, some nodes that have not been upgraded cannot verify the blocks proced by the upgraded nodes, and usually the hard fork will occur
23, soft forking
when the new consensus rules are released, nodes that have not been upgraded will proce illegal blocks because they do not know the new consensus rules, which will lead to temporary forking
24, hash -- hash value
generally translated as "hash", but also directly transliterated as "hash". In short, it is a function that compresses messages of any length to a message digest of a fixed length
25, main chain
the word "main chain" comes from the main network (, relative to the test network), that is, the officially online and independent blockchain network
for those who don't know the "jargon" in the currency circle, let's learn it as soon as possible:
1. What is legal currency legal currency is legal tender, which is issued by the state and the government. It is only guaranteed by the government credit, such as RMB, US dollar and so on 2. What is a token token, usually translated into token. Token is one of the important concepts in blockchain. Its more well-known name is "token". However, in the view of professional "chain circle" people, its more accurate translation is "token", which represents a proof of rights and interests on the blockchain, rather than currency token one is digital proof of rights and interests, which must be in the form of digital certificate of rights and interests, representing a right, an inherent and intrinsic value
3. What is warehouse building
the establishment of a position in a currency circle is also called opening a position, which refers to a trader's new purchase or sale of a certain amount of digital currency
What is Sohasuoha refers to investing all the principal
What is airdrop
airdrop is a very popular marketing method of cryptocurrency. In order to let potential investors and cryptocurrency enthusiasts get token related information, token teams often air drop tokens
6. What is lockup position locking generally refers to investors opening a new position opposite to their original position when the market moves in the opposite direction after the sale and purchase contract, which is also called lock, lock order, or even butterfly double flying doughnut candy is a kind of free digital currency issued to users when all kinds of digital currencies are just issued in ICO. It is a kind of momentum and publicity of the project itself by the issuers of virtual currency projects
breaking refers to falling below, and issuing refers to the issuing price of digital currency. Broken currency circle refers to the price of a digital currency falling below the issue price
What is private placementprivate placement is a way to invest in cryptocurrency projects, and it is also the best way for cryptocurrency project founders to raise funds for platform operation
What do you think of the K-line diagram
K-line chart is also called candle chart, Japanese line, yin-yang line, bar line, red and black line, etc., commonly referred to as "K-line". It is based on the opening price, the highest price, the lowest price and the closing price of each analysis cycle
What is hedging
General hedging refers to two transactions which are related to the market, opposite in direction, equal in quantity and balanced in profit and loss. In the futures contract market, buy the same number of positions with different directions. When the direction is determined, close out the positions in the opposite direction and keep the positive direction to make profits
What is the positionposition is a kind of market agreement, which promises the initial position of the sale and purchase contract, and the buyer is long and in the expected position; The selling contract is short and in the expected position
What are the advantagesgood news: refers to the news that the currency gets the attention of the mainstream media, or a breakthrough in the application of a technology, which is concive to stimulating the price rise
14. What is bad news
bad news: news that causes the price of bitcoin to fall, such as technical problems of bitcoin, central bank's crackdown, etc
What is reboundthe phenomenon of currency price rising e to rapid decline in the downward trend. The recovery is less than the decline
What is leverage
leverage trading, as the name suggests, is to use small amount of funds to invest several times the original amount, in order to obtain multiple returns or losses relative to the fluctuations of the investment object
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.
bitcoin is a typical blockchain system, which can be studied carefully
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swiping orders is a kind of cheating behavior in which the store pays someone to pretend to be a customer and improves the sales volume and ranking of the online store through fictitious transactions, so as to attract more customers. This kind of behavior of cheating consumers widely exists in o2o and other e-commerce instries
once a business operator is found to make false or misleading commercial propaganda on its goods, or assist other business operators in making false or misleading commercial propaganda by organizing false transactions, the supervision and inspection department shall order it to stop the illegal act and impose a fine of not less than 200000 yuan but not more than 1 million yuan; If the circumstances are serious, a fine of not less than one million yuan but not more than two million yuan shall be imposed, and the business license may be revoked. Any business operator who violates the provisions of Article 8 and publishes false advertisements shall be punished in accordance with the provisions of the advertising law.
I remember when I was a child, we watched a lot of Hong Kong TV dramas , such as "beating the Golden branch with drunkenness" and "the desire for evil in the Golden branch". We can't forget Liu Sanhao and Yao Jinling. However, as we grow up, we find that TVB TV dramas are not very popular! In fact, it's not. The development of entertainment is too fast. Hong Kong has not been integrated. We know what many actors look like, but we don't know their names
In fact, if we go back ten years now, those Hong Kong TVB actors who come to the mainland to shoot TV dramas may be popular, but the development of internal entertainment is too fast, and now there is no place for them. You can only say that they have not grasped the opportunity. It's a pity, but it's reasonable, After all, now that the entertainment instry is mature and Hong Kong stars are involved, in fact, it's better to stay in Hong Kong for development. After all, the entertainment instry in Hong Kong is also mature