What is double flower in the world of bitcoin

2.

The earliest is a kind of network virtual currency. It is characterized by decentralization, anonymity, and can only be used in the digital world. It does not belong to any country or financial institution, and is not subject to geographical restrictions. It can be exchanged anywhere in the world. Therefore, it is used as a money laundering tool by some criminals. In 2013, the U.S. government recognized the legal status of bitcoin, making the price of bitcoin soar

< H2 > extended information:

bitcoin is e-cash similar to e-mail. 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

starting from the essence of bitcoin, the essence of bitcoin is actually a special solution generated by a bunch of complex algorithms. A special solution is one of the infinite (in fact, bitcoin is finite) solutions that can be obtained from the equations. Every particular solution can solve the equation and is unique

many websites for technology players have begun to accept bitcoin transactions. Websites such as mtgox and btcchina, as well as some Taobao stores, can even accept services such as bitcoin exchange for us dollars and euro. There is no doubt that bitcoin has become a real currency in circulation, rather than a virtual currency like Tencent Q coin

3.

Bitcoin mining is a process that uses computer hardware to calculate the location of bitcoin and obtain it

mining is an incentive process to record data in the bitcoin system. In the bitcoin system, indivial users have the right to pack blocks after calculating a specific hash value by using CPU or GPU to hash

and in order to reward this user for packing blocks, the system will give a certain amount of bitcoin as reward. Because this process is very similar to "mining" in real life, most people call this process mining. In addition to bitcoin, other electronic virtual currencies can also be obtained through mining rewards, such as Ethereum, Monroe and so on

extended data:

mining risk:

1, currency security

the withdrawal of bitcoin requires hundreds of keys, and most people will record this long string of numbers on the computer, but frequent problems such as hard disk damage will make the key permanently lost, which also leads to the loss of bitcoin

2, system risk

system risk is very common in bitcoin, and the most common one is bifurcation. Bifurcation will lead to a drop in currency price and a sharp drop in mining income. However, many cases show that the forking will benefit the miners, and the forked competitive currency also needs the miners' computing power to complete the minting and trading process. In order to win more miners, the competitive currency will provide more block rewards and handling charges to attract miners. Risk makes miners

4. In the process of learning blockchain, you will hear the word "double flower", which means double payment, or more directly, a sum of money has been spent twice. In this article, we will briefly analyze why there are double flowers and how bitcoin can avoid double flowers

in the traditional transaction, there is no double spending problem because there is a centralized institution such as a bank: every payment will be dected from your bank account, and all details will be recorded in the bank. But in bitcoin, because there is no concept of account, utxo is introced, that is, no transaction output is spent. Because there is no guarantee from centralized institutions such as banks, when a transaction occurs, there may be a risk of double spending: for example, a has a bitcoin, and then he constructs two transactions T1 and T2 at the same time to spend the bitcoin, one of which is given to B, to buy a suit from B, one is given to C, and to buy a pair of shoes from C. If we do not introce some mechanism to avoid this situation, bitcoin, as a digital currency, will not have any meaning of existence. Next, let's analyze how bitcoin can prevent this "double flower" attack

(1) normal situation

first of all, let's look at the normal situation. To put it bluntly, most of the time, the consensus mechanism of blockchain can nip Shuanghua in the bud. Let's illustrate with the above examples:

suppose that a constructs two transactions T1 and T2, and transfers its own value of 1btc utxo to B and C respectively, in an attempt to obtain benefits from B and C at the same time. Then a broadcasts the two constructed transactions to the network almost at the same time

suppose that the miner node in the network receives the transaction T1 first, and finds that the source of funds for the transaction has not been spent, so it adds T1 to its own memory transaction pool and waits to be packaged into the block

in most cases, the miner node will receive transaction T2 soon. At this time, the miner node will refuse to process the transaction because the transaction input that T2 points to is the same as T1 that has been added to the transaction pool. Other miner nodes in the network are similar, so a's attempt to double flower is stillborn

(2) bifurcation

the above is normal, but there are also abnormal cases to consider: suppose that the miner nodes M1 and M2 dig out the block almost at the same time, and unfortunately M1 only receives transaction T1 when digging in the block, while M2 only receives transaction T2 when digging in the block, so transaction T1 and T2 are packed into two blocks respectively. Because these two blocks were g out at about the same time, resulting in the bifurcation of the blockchain:

some nodes in the network (which may be close to M1) received the block blk1 packed by M1 first, so they used the block to extend their own blockchain, while other nodes (which are close to M2) received the block blk2 packed by M2 first, and used the block to extend their own blockchain, So the whole blockchain network

5. Analyzing the advantages of LBTC from the perspective of code mechanism
dpos mechanism
in recent years, e to the resource waste of pow, unstable block output, and the existence of computing power attack, although POW is recognized as the most widely used and secure consensus mechanism, there is still a great risk of being attacked for the block chain with insufficient computing power in the whole network. More and more consensus mechanisms are proposed to be used in blockchain projects for trial and experiment. Dpos is one of the mainstream consensus mechanisms, and LBTC has adopted this mechanism. Dpos ensures that the voting right is in the hands of the coin holder, so the coin holder will be able to choose whether to pass the motion by voting, so as to determine the development direction of the project. At the same time, it also means that the development direction of the project depends on the hands of the people who care about the project itself, and the power of wisdom will promote the better development of the project. At the same time, the advantages of dpos mechanism are that there is no computing power attack, strictly abide by the time block and save resources
dpos advantages of LBTC
the dpos mechanism of LBTC also has its own characteristics: the number of nodes of LBTC is 101, compared with 21 or 51 nodes, the coin holder can vote for 51 nodes at most once in the wallet of LBTC, which further reces the risk of centralization; LBTC can output blocks stably in 3 seconds, and the block size of 2m ensures that LBTC is 400 times more efficient than bitcoin, and the transaction speed can reach more than 2000 transactions per second; The most important difference between LBTC and other projects is that LBTC's dpos mechanism has the rule of irreversible block. When the number of block agents reaches 90% or more in one round, or when the number of block agents exceeds 70%, the first block in the previous round can be considered as irreversible, so as to prevent bifurcation
LBTC's defense measures
in addition to dpos consensus mechanism, LBTC's technical level has other highlights
first of all, LBTC can prevent [replay attack]. What is a replay attack? Each bitcoin account will have a corresponding number of lbtcs based on its bitcoin balance. If the address, private key, algorithm, etc. on each chain are the same, and the transaction format is the same, the transaction initiated on one blockchain can be put on another blockchain for rebroadcasting, and may also be confirmed. This is the "replay attack.". In short, when a user transfers LBTC, BTC may also be transferred at the same time. LBTC modifies the hash algorithm in transaction signature. In the hash algorithm, "LBTC" field is added to LBTC. The hash generated by LBTC and BTC will be different. LBTC and bitcoin do not recognize each other's transactions, so as to prevent replay attacks
secondly, to prevent [forged mining]. There are no concepts of voting and balance in bitcoin transaction. In order to maximize the stability of LBTC, a new output composed of OP return is added in coinbase transaction. Op-return data is composed of three fields: publickey, time and sign (time). Time represents the timeliness of transaction. Publickey verifies sign (time), which is the principle of asymmetric encryption algorithm to prevent forgery and mining. LBTC has 101 nodes. Assuming that the attacker has 30 nodes, if the remaining 71 nodes are forged, other nodes can mistakenly think that the attacker's chain is the longest and block out. This is a forgery mining attack
thirdly, prevent [double flower attack]. Double spending attack is a money spent twice, it can also be called double payment attack. For example, BTG, which has attracted wide attention before, recently suffered 51% attacks. A malicious miner obtained at least 51% of the computing power of the BTG network, temporarily controlled the BTG blockchain, quickly raised money after recharging the exchange, then reversed the block, and successfully implemented Shuanghua. Due to the irreversible block mentioned above, when the transaction of LBTC block is confirmed, it is impossible to roll back, so as to prevent the double flower attack
Fourth, multithreading. In LBTC's transaction consistency and legitimacy check, the data that can be merged and integrated are merged and executed by multi thread, which greatly improves the transaction efficiency and enhances the performance of LBTC
code logic of LBTC
in addition, in terms of code logic, LBTC is divided into protocol layer, consensus layer and application layer. When it is necessary to transfer value, the transaction is completed through the protocol layer link and consensus layer. This process can not only be used as the exchange of value, but also as the value intermediary in the tripartite connection. The application layer is mainly based on smart contract. In the future, LBTC will realize the function of gateway based on smart contract. The payment gateway implements asset issuance, asset transaction, currency exchange, chain interaction and so on
that's why LBTC can say that it wants to do global value internet protocol. Through the payment gateway, it can exchange any currency, not only between currencies, but also between legal currency and digital currency. Isn't that very convenient? One click conversion is to buy eth with vnd and transfer it to her British cousin in the distance. She dislikes it and immediately changes it to EOS. After one second, it is changed to pound sterling. There is no need for extra conversion steps. It's good to get it in one step? Such an analysis, in fact, from the technical code level analysis of LBTC is quite reliable. However, compared with those experts, Xiaobian won't deceive you. Whether LBTC can realize decentralized value Internet Protocol in the future, focusing on code will be a more intuitive way GitHub of LBTC: https://github.com/lbtcio/lbtc-core
how to use gateway
next, we talk about the specific implementation of the gateway's "conversion and circulation", which can be roughly divided into three kinds:
first, after the LBTC system has built the gateway technology, with the gateway as the bridge, user a can convert any currency into LBTC, and then send it to any user B who wants to send it, while user B can convert LBTC into any currency he needs, Does this sound like what you usually do on the exchange? I think this is one of the reasons why LBTC proposes to be a "decentralized exchange"
Second, user a can deposit the funds in the gateway trusted by user B and transfer them to user B through the gateway
thirdly, LBTC will provide the function of "any user can issue token" in the early stage of gateway construction. Therefore, in the LBTC system, if user a has a good reputation, is recognized by everyone, and issues its own a token (of course, it should include the asset chain realized by asset mortgage), a can use its own a token for user B's currency exchange. After that, user a can redeem the a token exchanged to B. A is the gateway role in the transaction process
in the process mentioned above, the functions of asset issuance, asset transaction, currency exchange and chain interaction are realized respectively
the gateway is similar to the function of a bank, which can mainly solve the problem of cross-border transfer. With the high TPS and low handling charge of LBTC, it will be very convenient to realize cross-border transfer. For example, if you need to remit money from China to the U.S., you need to remit RMB to China's LBTC gateway, and then the U.S. gateway will receive the LBTC from China's gateway, convert it into U.S. dollars, and forward it to the U.S. account. In the above gateway system, it can be concluded that both payment parties do not need to join the network, just need to trust the gateway
although the gateway solves the problems of slow speed and high handling charge of traditional transfer payment, it also faces new problems
then there is a problem
in addition to the standard institutions or project parties invited by LBTC can become gateways, ordinary users can buy and sell with each other (in fact, this kind of behavior is more inclined to loan, if it is only the business between acquaintances, it will form a small independent network), How to prove that gateway is a trustworthy organization or indivial
how to extend the gateway of LBTC to cooperate with large organizations is obviously a problem for the team. Ripple has developed more mature. At present, it has cooperated with MUFG in Japan, Westpac in Australia and Standard Chartered Bank in the UK. With ripple, star currency and other payment digital currencies in front, LBTC needs to have more characteristics if it wants to go out of its own route. This can be expected in the later intelligent contract route planning
however, ripple is also accused of being too centralized because of its distribution mode. LBTC has 101 nodes because of its dpos mechanism, and because it is a bifurcated coin, it will be distributed to bitcoin holders 1:1 when it is issued. This can be said to be the inherent advantage of LBTC - it has wide dispersion. If it can be supported and recognized by the public in the future, it can reach a consensus, Then it will form a congenital advantage of wide distribution
in addition, how can we prove that assets really exist in reality and can be used as collateral in the process of asset chain? In addition to large-scale institutions such as banks, small-scale network also has its inevitability. The proof of assets on the asset chain is a very important part. If it is not regulated and certified, it is very likely that the gateway will run away or false gateway will occur. Although the gateway is exemplified as "Taobao" platform, in theory, the platform can not manage the business content, but the platform has supervision on the quality of goods, otherwise it will cause confusion
decentralized exchanges
let's go back to the first point and talk about my ideas on decentralized exchanges. At present, mines and centralized exchanges are the protagonists in the early development of blockchain. With the rise of more and more exchanges, centralized exchanges fall into manipulation scandals and so on, which bring room for the growth of decentralized exchanges. Decentralized transaction is very likely to bring value to the field of blockchain and become the real protagonist in the era of blockchain. With gateway technology, LBTC can realize decentralized exchange. In the decentralized exchange of LBTC, the user's own currency will be kept by himself, which prevents the possibility of losing the currency in the centralized exchange. At the same time, it can also prevent the opaque system transactions, operational and technical risks. According to the previous gateway interview, LBTC will also work with reliable project parties to put on the stock exchange for the benefit of all community members. Generally speaking, LBTC's development route is relatively clear, and its goal in the field of payment is also very clear. Hold on, partners, the future is promising!

6.

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

7. Because it comes from money. Virtual money is bought with real money. So it's also called coin there.

8. If you download apps, you can download them directly from the app market, but some apps that have not been put on the shelves can be downloaded directly from the browser.

9. The concept of bitcoin was first proposed by Nakamoto in 2009. According to Nakamoto's idea, open source software was designed and released, and P2P network was built on it. Bitcoin is a kind of P2P digital currency. Point to point transmission means a decentralized payment system
unlike most currencies, bitcoin does not rely on specific currency institutions. It is generated by a large number of calculations based on specific algorithms. Bitcoin economy uses a distributed database composed of many nodes in the whole P2P network to confirm and record all transactions, and uses cryptography design to ensure the security of all aspects of currency circulation. The decentralized nature and algorithm of P2P can ensure that it is impossible to artificially manipulate the value of bitcoin through mass proction. 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. The monetary system used to have no more than 10.5 million in four years, after which the total number will be permanently limited to 21 million
bitcoin can be cashed and converted into the currency of most countries. Users can use bitcoin to buy some virtual items, such as clothes, hats and equipment in online games. As long as someone accepts it, they can also use bitcoin to buy real-life items
currency characteristics
Decentralization: bitcoin is the first distributed virtual currency, and the whole network is composed of users without a central bank. Decentralization is the guarantee of bitcoin's security and freedom
Global Circulation: bitcoin can be managed on any computer connected to the Internet. No matter where you are, anyone can dig, buy, sell or collect bitcoin
exclusive ownership: the private key is required to manipulate bitcoin, which can be stored in any storage medium in isolation. No one can get it except the user himself
low transaction cost: bitcoin can be remitted free of charge, but a transaction fee of about 1 bitfen will be charged for each transaction to ensure faster transaction execution
no hidden cost: as a means of payment from a to B, bitcoin has no cumbersome quota and proceres. If you know the other party's bitcoin address, you can pay
cross platform Mining: users can explore the computing power of different hardware on many platforms.

10. Not too clear,