Blockchain 12306
bitcoin cash BBC can be said to be a variant of bitcoin. Bitcoin is said to have a limited number, only 21 million, but the real number can not be verified. At present, the fission of the cash BBC makes people believe that bitcoin can be infinitely fission
the essence of currency is a combination of national strength and credit. Bitcoin, as a virtual currency, has no guarantee or endorsement from any country and no legal protection
If a country's currency does not have enough national strength to guarantee its credit, it can only rely on the old hard currency: gold
gold is credit
at that time, with the emergence of bitcoin, some people thought that the golden age had passed, so they compared the emergence of bitcoin to mining. However, there was only one thing in the world called gold, and more than n Ethernet coins, Wright coins and so on appeared around bitcoin. Such virtual currencies can invent countless varieties
it can be imagined that once the virtual currency is destroyed, the real currency gold will lead to long-term good
1. At present, the biggest positive factor for gold is the US dollar. Recently, the continuous decline of the US dollar has made gold form a w double bottom
2. The second relationship of gold is international geopolitics. Any disturbance can make gold as a hedge fund soar
The third related account of gold is the world's hard currency. When a country's currency collapses, unless you have the world's hegemonic currency such as the US dollar, only gold can let you avoid this super risk At present, China's gold reserves have quietly ranked second in the world, from 1000 tons in 2009 to more than 4000 tons at present. Some people expect that in three years, China's gold reserves will surpass the United States and jump to the first place in the world According to the data recently released by the China Gold Association, China's gold bar consumption in the first half of 2017 rose by 51.09% to 158.40 tons year on year, and the national gold consumption rose by 9.89% to 545.23 tons year on year! Because the private sector has more than 1600 tons of gold reserves In 2013, some experts pointed out that China's national gold reserve should be more than 5000 tons, and once a currency war broke out, it could occupy a favorable position On the one hand, the internationalization of RMB is guaranteed by the comprehensive strength of the country; on the other hand, it has a lot of gold reserves
gold is a combination of money, finance and commodity. It has become a belief of natural currency for thousands of years, and the future of gold is worth looking forward to
thank you
let's talk about the problem of high concurrency. High concurrency is a problem in the computer field. In short, the problem of high concurrency is that the system cannot run multiple tasks at the same time smoothly
many tasks are running at the same time, and a large number of users rush in. The system can't bear so many tasks. There will be high concurrency problems, and your system will be stuck, just like the 12306 system is always stuck ring the Spring Festival, which may be caused by the high concurrency problems
the traditional Internet still has the problem of high concurrency, which naturally exists in the blockchain network. After all, the maturity of the blockchain is still far behind that of the traditional Internet. However, if there is no safe, reliable and efficient public chain, the development of the whole blockchain instry will be seriously restricted, and the application landing is empty talk
in this context, DAG technology has been proposed, DAG's full name is "directed acyclic graph", which is translated into "directed acyclic graph" in Chinese
What's the matter with DAG directed acyclic graph and what role it can play? Let's explain< Dag: a new data structure
DAG, Chinese name is "directed acyclic graph", literally, "directed & quot; That is to say, it has direction,
"no loop" means that it has no loop and cannot form a closed loop. Therefore, DAG is actually a new type of data structure. This data structure has direction and can not form a closed loop
in terms of traditional blocks, we always take "block" as the unit, and a block often contains multiple transaction information. In DAG, there is no concept of block. Instead, it takes "unit" as the unit. Each unit records the transaction of a single user. The unit is not a block, but a transaction. In this way, the time of packing blocks can be saved
in short, the biggest difference between blockchain and DAG directed acyclic graph is that blockchain is one block after another to store and verify the distributed ledger of transactions, while DAG regards each transaction as a block, and each transaction can be linked to multiple previous transactions for verification< Second, the working principle of DAG
in the traditional blockchain, take bitcoin as an example, it is a single chain structure. The blocks are arranged according to the time stamp sequence (as shown in Figure 1), and the data is recorded on a main chain. To use an inappropriate metaphor, this "single chain" structure is a chain arranged word by word
there is only one single chain in the blockchain, so it can not be executed concurrently when the block is packaged. The new block will be added to the original longest chain, and all nodes will follow the longest chain and continue to spread infinitely in the order of timestamp. For DAG, each newly added unit is not only added to one unit of the longest chain, but also to all previous units (as shown in Figure 2)
for example: suppose I publish a new transaction, and there are two effective transaction units in DAG structure, then my transaction unit will actively link to the previous two at the same time to verify and confirm until it is linked to Genesis unit, and the hash of the previous unit will be included in its own unit
in other words, if you want to make a transaction, you have to verify the previous transaction, specifically several transactions, according to different rules. This verification method enables DAG to write many transactions asynchronously and concurrently, and finally forms a topological tree structure, which greatly improves the scalability
according to DAG directed acyclic graph, every transaction is directly involved in the maintenance of the whole network. When the transaction is initiated, the whole network is broadcast directly, skipping the block packing stage. In this way, the time of block packing is saved, and the transaction processing efficiency of the blockchain is improved
with the increase of time, the blockchains of all transactions are interconnected to form a graph structure. If you want to change the data, it is not just the problem of several blocks, but the data change of the whole block diagram. Dag is more complex and difficult to change
to sum up, DAG, as a new type of decentralized data structure, belongs to a kind of generalized blockchain and has the attribute of decentralization. However, the differences between the two are as follows:
the composition unit of blockchain is block and the composition unit of DAG is TX
blockchain is single threaded, DAG is multi-threaded
all transactions of blockchain are recorded in the same block, and each transaction of DAG is recorded in each transaction separately
blockchain needs miners, DAG doesn't need miners< (3) representative of DAG: iota is undoubtedly the most famous representative project of DAG. It can be said that it is precisely because iota, the currency, broke into the fourth place in market value in the second half of 2017 that people really realized its underlying technology: DAG directed acyclic graph
iota puts forward the concept of "entanglement" on the basis of DAG directed acyclic graph. In iota, there is no concept of block, and the minimum unit of consensus is transaction. Each transaction will refer to the past two transaction records hash, so that the previous transaction will prove the legitimacy of the past two transactions and indirectly prove the legitimacy of all previous transactions. In this way, a small number of nodes such as miners in the traditional blockchain are no longer needed to verify transactions and package blocks, so as to improve efficiency and save transaction costs< Fourth, the current situation of DAG
although DAG directed acyclic graph can make up for some disadvantages of traditional blockchain in theory, it is not mature at present, and it has been applied to the field of digital currency for a short time
it did not take as long as 10 years to verify the security of the whole system as bitcoin did, nor did it achieve a wide range of application scenarios as Ethereum did. However, some voices now propose to adopt the data structure of "traditional blockchain + DAG", but there is no outstanding case, so I won't say more here
to sum up, in this section, we introce the derivative technology of blockchain: DAG directed acyclic graph, which is a new data structure, and can significantly improve the efficiency and power of blockchain transaction processing.
Wechat payment can't be made after the amount of change exceeds 100000 yuan. You need to remove the account protection before you can use it
wechat payment is a payment function integrated in wechat client, users can complete the fast payment process through mobile phone. Wechat payment is based on fast payment with bank card, providing users with safe, fast and efficient payment services. Since November 23, 2017, wechat payment service function has been running on the 12306 website of China Railway Customer Service Center
on April 1, 2018, when consumers use wechat wallet to scan the static barcode for payment, the upper limit of single day zero wallet payment is no more than 500 yuan, and all bank cards associated with wechat can also independently obtain the upper limit of 500 yuan. In March 2018, license plate = payment code, wechat directly launched "high speed E-line". On June 29, 2018, wechat payment and Michelin Guide announced strategic cooperation in Guangzhou
on December 11, 2018, the "intelligent tax laboratory" jointly built by Shenzhen Taxation Bureau of the State Administration of Taxation and Tencent successfully connected the blockchain invoice system with wechat payment platform, and launched the function of issuing blockchain invoice through wechat payment for small and medium-sized micro enterprises with wechat payment and invoice use needs, Blockchain e-invoice began to enter the daily life of ordinary people
Wechat payment to be cancelled on September 15 is fake
wechat payment is a payment function integrated in wechat client, users can complete the fast payment process through mobile phone. Wechat payment is based on fast payment with bank card, providing users with safe, fast and efficient payment services. Since November 23, 2017, wechat payment service function has been running on the 12306 website of China Railway Customer Service Center
extension:
WeChat payment has achieved credit card payment, scan code payment, official account payment, APP payment, and provides new marketing tools such as enterprise red envelopes, vouchers, and reced discount to meet different payment scenes of users and merchants. p>
on December 11, 2018, the "intelligent tax laboratory" jointly built by Shenzhen Taxation Bureau of the State Administration of Taxation and Tencent successfully connected the blockchain invoice system with wechat payment platform, and launched the function of issuing blockchain invoice through wechat payment for small and medium-sized micro enterprises with wechat payment and invoice use needs, Blockchain e-invoice began to enter the daily life of ordinary people