Repeated spending of bitcoin

1. The concept of bitcoin was first proposed by Nakamoto on November 1, 2008, and was officially born on January 3, 2009. According to the idea of Nakamoto, the open source software is designed and released, and the P2P network on it is constructed. Bitcoin is a virtual encrypted digital currency in the form of P2P. Point to point transmission means a decentralized payment system
unlike all currencies, bitcoin does not rely on a specific currency institution to issue. It is generated by a large number of calculations based on a specific algorithm. 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.

2. After six confirmations, the probability of double flower is almost zero

3. As a financial technology enthusiast, kuanke online Xiaobian, I think, there are several major factors to promote
1, the short-term factors that determine the price: supply and demand and market sentiment
the relationship between supply and demand means that if the amount of money spent on buying bitcoin is more than that spent on selling bitcoin, the price of bitcoin will rise. If more people buy bitcoin, it will rise
market sentiment refers to the views of the market and the media on the price trend of bitcoin at that time. When many people strongly see bitcoin, the market sentiment is confident, and the price of bitcoin will rise rapidly. If the media makes pessimistic reports on the price of bitcoin, it will affect people's confidence and lead people to sell bitcoin, and the price of bitcoin will fall
2, the medium-term factors that determine the price: policy, news and mining cost
on the policy side, it is the policy attitude of governments towards bitcoin. For example, the recent crackdown and regulation of bitcoin by the South Korean government has led to a sharp drop in the price of bitcoin in the near future. If more and more countries support and encourage the development of bitcoin, the price of bitcoin will be higher and higher. On the contrary, if many countries begin to suppress bitcoin, the price of bitcoin will continue to fall
on the news side, there are some important things in the bitcoin instry. For example, around December, the two major stock exchanges in the United States launched bitcoin futures, which are good for bitcoin and directly push the price of bitcoin up to about $20000
mining cost is the cost of bitcoin miners using machines to dig out bitcoin. At present, the cost of digging out a bitcoin is about 12000 US dollars, so it is difficult for the price of bitcoin to fall below 12000 US dollars. Mining cost is the bottom line of bitcoin price. With the continuous increase of mining costs, the reason is that more competitors enter the mining field, especially many large institutions, companies and countries
3 determines the long-term price factors: the US dollar trend, the global bubble, the official digital currency, and the block chain technology.
the trend of the US dollar. According to the personal analysis data, the US dollar will weaken in the next few years, which means that the global monetary system with us dollar as the world currency in the past will be rebuilt. The rise and future of bitcoin is to assume the identity and mission of the world currency
global bubble. Since the United States abolished the gold standard Bretton Woods system in 70s, many countries in the United States have been printing banknote printing machines. The bubble of currency has caused the global economic bubble and asset bubble. The global economic crisis triggered by the US subprime mortgage crisis in 2008 is the crisis triggered by the currency bubble. At present, the global economic bubble and asset bubble have reached the critical point of collapse. The birth of bitcoin was e to the reason of the currency bubble, which made people no longer believe in the currency of national credit, and began to believe and recognize bitcoin.
official digital currency, countries around the world have begun to prepare to issue official digital currency, that is, digital currency issued by countries. Venezuela has issued a national level digital currency - Petroleum currency. Israel is preparing to issue it, Russia is also preparing to issue it, and the Japanese government is issuing it. 2018 will become the first year of the global official digital currency. The accelerated launch of official digital currency and its increasing popularity show that the value of bitcoin as internet currency is unlimited.

4.

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

5. The owner of the building is energetic and seems to be able to do a counter experiment; Don't connect the computer to the Internet. Take a wallet from an external USB flash drive and put it in to see if it can show how much money there is? In fact, the experiment in front of you should not be that the wallet can automatically generate a new address without networking, but that there are a large number of hidden change old addresses of your own in it. However, a large number of hidden change old addresses should be in the wallet.dat file, not in the empty wallet terminal software.

6. The solution to the equation is mining, the transaction is block, and each address will not be repeated

7. can't. Less miners will only lead to less proction. Repeated payment is a bug that bitcoin cannot tolerate

8. Theoretically, it is possible, but the current human computer technology does not achieve such high performance, therefore, it is almost impossible to use traditional technology to crack. With the development of quantum technology, the current encryption technology is likely to be completely cracked, including bitcoin algorithm, RSA encryption and so on.

9. There are two main cases of double payment: one is to let the miner help to achieve, the other is to become a miner. In November 2013, we found that betcoin has double payment in ghash.io mine pool, and every transaction used by the website can be carried out without waiting for confirmation<
solution:
analyze transaction risk
payment channel
signed by trusted third party
remote authentication
ID verification
block waiting for confirmation
punish double payment