Engineering BTC

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. Bitcoin technology, including protocols and cryptography, has a strong security record, and bitcoin network is perhaps the largest distributed computing project in the world. The most common weakness of bitcoin is user error. The bitcoin wallet file that stores the private key may be accidentally deleted, lost or stolen. This is very similar to physical cash stored electronically. Fortunately, users can use reliable security policies to protect their funds, and they can also use providers who provide good security levels and theft or loss insurance services

in fact, safety is not safe but has the final say in practice.

3. BTC (buttress thread coupling) trapezoidal thread coupling is an API standard thread connection type, which is commonly used in the connection of petrochemical pipes or tools, such as floating collar, guide shoe and pipe shoe used in cementing operation. The pitch is 8 teeth per inch and the tooth height is 1-1.2 mm. The external thread part 1 is designed with - 15 ° The end face shoulder 4 is connected with - 15 of internal thread part 2 after tightening ° Internal torque shoulder interference fit, after the internal and external threaded parts are tightened, at least one circle of threads closely fit, the top surface of thread teeth of threaded parts is parallel to the oil pipe axis, and the inner diameter D2 of internal thread 2 is approximately the same as that of external thread 1. Trapezoidal thread has excellent sealing performance, high connection strength and good anti torque make-up ability, so it can be used as an alternative to thickened thread or replace thickened thread in practical engineering

4.

1. The nature of the two currencies is different: bitcoin is an encrypted digital currency, and Morgan is a typical MLM currency

(1) bitcoin is a consensus network, contributing to a new payment system and a fully digital currency. It is the first decentralized peer-to-peer payment network, which is controlled by its users without a central management organization or middleman

(2) Morgan is a kind of typical MLM currency, they often promise high income, the information of the founding operation team is not open, and they have the background of international large companies, so they put forward a set of seemingly reasonable economic theory

extension data: the harm of

network currency: the extensive application of

1 and virtual currency is also accelerating the rampant network robbers.

(1) in December 2006, the Shenzhen Public Security Bureau announced that it had cracked the country's largest theft network virtual property case, and 11 suspect was arrested. The gang used trojan virus to illegally steal virtual property such as tens of thousands of QQ numbers and QQ coins, and sold stolen goods on the network, making a profit of more than 700000 yuan

(2) in this case, the virtual currency Q was used as the standard of conviction and sentencing, and the police's arrest of illegal elements on suspicion of theft is a special case. The reason is that Tencent has filed with the Guangdong Provincial Price Bureau, and one q is equivalent to 1 yuan

(3) online currency is used more and more widely, for example, it can be used to buy anti-virus software online, vote for super girl, and some websites even use online currency to pay the moderator

2. Outside the business system, because indivial virtual currency has become the "equivalent" of RMB, or even "online RMB", which shows the role of "network hard currency", the illegal gains of illegal gambling can be cashed into RMB, which further promotes online gambling