Bitcoin central structure

1. In order to understand the technical principle of bitcoin, we need to understand two important cryptographic techniques: hash code: it converts a long string into a fixed length string, and its conversion is irreversible, that is, it is impossible to guess the original string from hash code. Sha256 is mainly used in bitcoin protocol
public key system: corresponds to a public key and a private key, keeps the private key in the application and publishes the public key. When Party A transmits information to Party B, it can use Party A's private key to encrypt the information, and Party B can use Party A's public key to decrypt the information, so as to ensure that the third party cannot impersonate Party A to send the information; At the same time, when Party A transmits information to Party B, it is encrypted with Party B's public key and sent to Party B, and then Party B decrypts it with his own private key, so as to ensure that the third party cannot eavesdrop on the communication between the two people. RSA is the most common public key system, but the lliptic curve digital signature algorithm is used in bitcoin protocol. What's the difference between cash and bank account? Bitcoin is an electronic currency in BTC. In this article, it is also used to refer to the whole bitcoin system. Like opening an account in a bank, the corresponding concept in bitcoin is address. Everyone can have one or more bitcoin addresses, which are used to pay and collect money. Each address is a string that starts with 1. For example, I have two bitcoin accounts, and. A bitcoin account is uniquely determined by a pair of public key and private key. To save the account, you only need to save the private key file. Unlike bank accounts, banks keep all transaction records and maintain the book balance of each account, while bitcoin's transaction records are jointly maintained by the whole P2P network through a pre agreed protocol. How much money is in my account address? Although the current account balance can be seen by bitcoin software, unlike banks, there is no place to maintain the book balance of each address. It can only calculate the account balance in real time through all historical transactions. How do I pay? When I pay from address a to address B of the other party, the payment amount is e. at this time, both parties will announce the transaction information to each network node, telling address a to pay to address B, and the payment amount is e. In order to prevent the third party from forging the transaction information, the transaction information will be encrypted with the private key of address A. at this time, the network node receiving the transaction information can use the public key of address a to verify that the transaction information is indeed sent by address a. Of course, trading software will help us do these things, we just need to input the relevant parameters in the software. What will the network node do after receiving the transaction information? This is the most important part of the bitcoin system, which needs to be elaborated. For the sake of simplicity, only bitcoin protocol has been implemented. In the current version, each network node will save all transaction information synchronously. There are two kinds of transaction information in history, one is & quot; Verified & quot; The transaction information, that is, the verified transaction information, is stored in a series of "blocks". Each & quot; block" Is the previous & quot; bock" The ID of each block is the hash code of the hash code of the block and the new transaction information (see an actual block). The other category refers to those who also & quot; Unverified & quot; The transaction information just paid above belongs to this category. When a network node receives new unverified transaction information (possibly more than one), it can calculate the book balance of each address at that time because the node keeps all the transaction information in history, so it can calculate whether the transaction information is valid, that is, whether there is enough balance in the payment account. After eliminating the invalid transaction information, it first takes out the last & quot; block" Then, the unverified transaction information is combined with the ID, and a verification code is added to form a new "block". It needs a lot of calculation to build a new block, because it needs to calculate the verification code, so that the above combination becomes a block, that is, the first several bits of the hash code of the block are 1. At present, the first 13 bits need to be 1 (generally, the specific method is uncertain), which means that if the block is generated by enumeration method, the average number of enumerations is 16 ^ 13. Using CPU resources to generate a block is called "gold mining", because the proction of the block will get a certain reward, and the reward information has been included in the block. When a network node generates a new block, it will broadcast to other network nodes. However, this network block may not be accepted by the network, because it is possible that other network nodes have proced the block earlier. Only the earliest block or the block with the largest number of subsequent blocks is valid, and the remaining blocks are no longer used as the initial blocks of the next block. How does the other party confirm that the payment is successful? When the payment information is distributed to the network node, the network node begins to calculate whether the transaction is valid (that is, whether the account balance is enough to pay), and attempts to generate blocks containing the transaction information. When six blocks (one direct block and five subsequent blocks) contain the transaction information, the transaction information is considered "verified", so that the transaction is formally confirmed, and the other party can confirm the successful payment. A possible problem is that I will pay the balance of address a to address B, and at the same time pay to address C. If I only verify that the single comparison transaction is valid. At this point, my way of cheating is to generate six blocks including B to B and six blocks including C to C before the truth is revealed. Because I need a very long CPU time to generate a block, compared with the whole network, the probability of my cheating success is very small. What is the motivation of network nodes to proce blocks? As can be seen from the above description, in order to make the transaction information effective, the network node needs to generate 1 and 5 subsequent blocks to contain the transaction information, and such block generation is very CPU intensive. How to let other network nodes help to proce blocks as soon as possible? The answer is very simple. The agreement stipulates that BTC will be rewarded for the address where the block is proced, as well as the Commission promised by both parties. At present, the reward for procing a block is 50btc, which will be halved every four years in the future. For example, the reward will be 25btc from 2013 to 2016. Is the transaction anonymous? Yes, and No. All bitcoin transactions are visible. We can check all transaction records of each account, such as mine. But what's different from the banking monetary system is that everyone's account itself is anonymous, and everyone can open many accounts. In general, anonymity is not as good as it claims. But bitcoin has another advantage in doing black market trading: it can't be frozen. Even if the police trace a bitcoin address, there is nothing they can do unless they trace the computer used by the exchange based on the Internet address. How to ensure that bitcoin does not depreciate? Generally speaking, in the case of equivalent trading activities, the value of money is inversely proportional to the amount of money issued. Unlike the traditional money market, the central bank can determine the amount of money issued. Bitcoin does not have a central issuing institution. Only by procing blocks can we get a certain amount of BTC currency. Therefore, bitcoin's new amount of money depends on: 1. The speed of procing blocks: bitcoin's agreement stipulates that the difficulty of procing blocks is fixed at an average of 2016 every two weeks, about 10 minutes. Moore's law of doubling CPU speed every 18 months will not speed up the proction of block. 2. The number of rewards for block proction: at present, 50 BTC is awarded for each block proced, which is halved every four years. In 2013, 25 BTC is awarded, and in 2017, 12.5 BTC is awarded. Considering the above two factors, bitcoin's currency issuing speed is not controlled by any single node in the network. Its protocol makes the currency stock known in advance, and the maximum stock is only 21 million BTC

2.

The capacity of a block in bitcoin is 1m (megabytes). A transaction is between 250 and 500 bytes

according to this algorithm, a block contains about 4194.3 transactions

the confirmation time of a block in bitcoin is 10 minutes, so the seven transactions that a block can process per second may sometimes be less than seven

What are the consequences

The bifurcations of

bitcoin are divided into hard bifurcations and soft bifurcations

hard fork means that when the block format or transaction format of bitcoin changes, the UN upgraded nodes refuse to verify the blocks proced by the upgraded nodes

the upgraded nodes can verify the blocks proced by the non upgraded nodes, and they continue the chain they think is correct, so they are divided into two chains

What is soft bifurcation

soft bifurcation means that when the data structure of bitcoin transaction changes,

UN upgraded nodes can verify the blocks proced by upgraded nodes,

and upgraded nodes can also verify the blocks proced by UN upgraded nodes

3.

In the discussion of blockchain, bitcoin and other digital currencies, we often hear the word "bifurcation". So what is bifurcation? What is the effect of bifurcation

blockchain

before talking about bifurcation, popularize a little knowledge of blockchain, so as to help us understand what bifurcation is more easily (if you don't have any concept of blockchain, please read my previous articles, which are all popular words to help you understand what blockchain is)

blockchain, as the name suggests, is a chain composed of blocks. Of course, this kind of chain is just a figurative metaphor. To put it bluntly, data blocks are connected orderly. In bitcoin, the transaction records of bitcoin are stored in the block. The size of the block and the space occupied by the transaction records determine how many transactions can be stored in a block. These transaction records are packaged into blocks, and then the blocks are connected one by one to form a blockchain

We know that bitcoin software, like other software, needs to be updated and modified regularly in order to make it better. So a new version will appear, but not everyone will download the new version, so one miner will run the old version, and some will run the new version. If the old and new versions are not compatible, the blockchain will bifurcate. Because there may be differences between the version blocks and the old version blocks, they cannot be connected to the same blockchain, so there will be two or even more chains, which is called bifurcation

soft forking

soft forking refers to that 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, resulting in temporary forking. This kind of bifurcation will be graally repaired with the upgrading of nodes

hard fork

hard fork refers to the permanent divergence of the blockchain. 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 hard fork occurs. Therefore, in the field of digital currency, hard bifurcation often leads to the emergence of new currencies. For example, the hard bifurcation of Ethereum led to the emergence of eth

What is bifurcation? What is bitcoin bifurcation

4. Forking is different from ordinary upgrading. Ordinary upgrading does not affect agreement consensus before and after upgrading, and generally does not need the participation of community consensus or computing consensus. According to the modification of the protocol, bifurcation can be divided into soft bifurcation and hard bifurcation

existing definition:

[lightning definition] hard fork refers to that when the bitcoin block format or transaction format (this is the widely spread "consensus" (should be part of the agreement consensus)) changes, the UN upgraded node refuses to verify the blocks proced by the upgraded node, but the upgraded node can verify the blocks proced by the UN upgraded node, Then we continue the chain that we think is right, so we divide it into two chains< A permanent divergence in the block chain, commonly occurs when non upgraded nodes can't validate blocks created by upgraded nodes that follow new consensus rules, The UN upgraded node can verify the blocks proced by the upgraded node, and the upgraded node can also verify the blocks proced by the UN upgraded node<

a temporary fork in the block chain which commonly occurs when miners using non upgraded nodes vialate a new consensus rule their nodes don't know about.

I don't think we can say which definition is right or wrong. The specific definition can be summed up according to the differences between the two that have been widely agreed in the community, and it doesn't need authority to specify

hard fork: without forward compatibility, the previous version will be unusable and need to be upgraded

soft fork: it has good compatibility, at least some functions of previous versions are available, and can not be upgraded

hard branching: at the level of blockchain, there will be two branching chains, one old chain and one new chain

soft bifurcation: there are no forked chains at the level of blockchain, but only the blocks that make up the chain, including new blocks and old blocks

hard forking: it is necessary to agree with the forking upgrade at a certain time point, and those who do not agree will enter the old chain

soft bifurcation: for quite a long time, it is allowed to continue to use the original version to generate old blocks and coexist with new blocks without upgrading

5. So what are nodes
a node is a network node in the blockchain distributed ledger system. By connecting servers, computers and other devices through the network, different types of blockchains have different ways to become nodes. For example, bitcoin participates in trading and mining, and EOS participates in election campaign to become a node
the following is what is a bitcoin full node
bitcoin full node is the node that downloads and preserves complete blockchain data by loading bitcoin clients (including bitcoin unlimited and bitcoin)
because of the congestion of the blockchain transaction network, the author solves the problem by adjusting the broadcast communication, information encryption and decryption, consensus mechanism and transaction verification mechanism. In the whole bitcoin network, from miners to ordinary users can be regarded as a node in the bitcoin network, but because bitcoin has the characteristics of multi centralization, In the whole network, its important role is "bitcoin all nodes."

6.

Every other time, the bitcoin system will generate a random code on the system node. All computers in the Internet can search for this code. Whoever finds this code will generate a block and get a bitcoin. This process is often called mining

at present, one bitcoin is divided into eight decimal places based on the current data structure, that is, 0.00000001btc. The smallest unit of bitcoin g by miners is 0.00000001btc

generally speaking, bitcoin is like a gold mountain with a total amount of 21 million gold coins. To get it, players need to use the computing power of the computer to calculate a group of numbers according to the existing algorithms

extended data:

unlike all currencies, bitcoin does not rely on specific currency institutions to issue. It is generated by a large number of calculations based on specific algorithms. Bitcoin economy uses the distributed database composed of many nodes in the whole P2P network to confirm and record all transactions, And the use of cryptography design to ensure the security of all aspects of money circulation

the decentralized feature and algorithm of P2P can ensure that it is impossible to artificially control the value of bitcoin by mass manufacturing. The design based on cryptography can make bitcoin only be transferred or paid by the real owner. This also ensures the anonymity of money ownership and circulation transactions. The biggest difference between bitcoin and other virtual currencies is that the total amount of bitcoin is very limited and it has a strong scarcity

7.

Transaction mode of bitcoin

bitcoin is e-cash similar to e-mail, and both parties need "bitcoin wallet" similar to e-mail and "bitcoin address" similar to e-mail address. Just like sending and receiving e-mail, the remitter pays bitcoin directly to the other party through a computer or smart phone according to the recipient's address. The following table lists some websites that download bitcoin wallets and addresses for free

a bitcoin address is a string of about 33 characters long, consisting of letters and numbers, always starting with 1 or 3, such as & quot& quot; Bitcoin software can generate address automatically, and it doesn't need to exchange information online, so it can be offline. More than 2 bitcoin addresses are available. Figuratively speaking, there are about two grains of sand in the world. If there is an earth in each grain of sand, then the total number of bitcoin addresses far exceeds the number of all the sand on all these "earths"

the bitcoin address and private key appear in pairs, and their relationship is just like the bank card number and password. A bitcoin address is like a bank card number, which records how much bitcoin you have on it. You can generate bitcoin address at will to store bitcoin. When each bitcoin address is generated, a corresponding private key of the address will be generated. This private key proves that you have ownership of the bitcoin at that address. We can simply understand the bitcoin address as the bank card number, and the private key of the address as the password of the corresponding bank card number. Only when you know the bank password can you use the money on the bank card number. Therefore, please keep your address and private key when using bitcoin wallet

after the transaction data of bitcoin is packaged into a "data block" or "block", the transaction is initially confirmed. When a block is linked to a previous block, the transaction is further confirmed. After six block confirmations in a row, the transaction was irreversibly confirmed. Bitcoin P2P stores all transaction history in a "blockchain.". The blockchain continues to extend, and once new blocks are added to the blockchain, they will not be removed. Blockchain is actually a distributed database composed of a group of scattered client nodes and all participants, which is a record of all bitcoin transaction history. Nakamoto predicts that when the amount of data increases, users hope that not all the data will be stored in their own nodes. In order to achieve this goal, he uses the hash function mechanism. In this way, the client will be able to automatically eliminate those parts that it will never use, such as some very early bitcoin transactions

8.

Last week, a paragraph about bitcoin became popular:

bitcoin broke through 5800 US dollars (about 38280 yuan) . When it was issued in 2009, 1 US dollar was equivalent to 1300 bitcoins. What is investment? It has increased by 7.54 million times in 8 years. At that time, you spent 38000 yuan to buy some bitcoin. Now you are the richest man in China, surpassing Xu Jiayin, who has 290 billion yuan

but just one week later, on October 20, bitcoin broke through the $6000 mark. Although it fell later, it reached more than $6000 again on October 21, reaching a maximum of $6147. In terms of $6000, bitcoin prices have risen 7.8 million times in eight years

according to cryptocompare, a bitcoin data provider, e to China's strict supervision of cryptocurrency trading, the global share of bitcoin market has been greatly changed. Now, in the total trading volume of the world's bitcoin exchanges, the trading volume of RMB versus bitcoin accounts for about 1.6%

} the proportion of RMB and yen in global bitcoin trading volume (photo source: cryptocompare)

the reporter noted that in the first half of this year, after Japan's legislation recognized bitcoin as a legal payment method, bitcoin's trading volume in Japan surged, and Japanese regulatory authorities have issued certificates to 11 cryptocurrency exchanges. About 58% of bitcoin trading currently takes place in the Japanese market, and nearly a third of yen to bitcoin trading takes place on the bitflyer exchange in Tokyo. In addition, the U.S. and South Korea markets also account for a large part of global bitcoin transactions - the U.S. dollar and the Korean won account for 27% and 7% of the total bitcoin transactions, respectively< br />