Sources of bitcoin Technology

Why does bitcoin have the characteristics of decentralization, unforgeability and tamperability?

Centralization requires a central institution similar to a bank to verify transactions. There is no center to verify the authenticity of transactions.

Decentralization enables all nodes to verify the authenticity of the transaction. What does it rely on to verify?

Asymmetric encryption technology is used. What is asymmetric encryption technology? It refers to the encryption algorithm using different keys when encrypting and decrypting. If encryption and decryption use the same key, we call it symmetric encryption. What's not safe about symmetric keys is that if you use the same key, it's not safe._DJMINER

For asymmetric encryption, the detailed description is that a sends information to B. A and B will produce a pair of public and private keys for encryption. A private key is like having a private key. Only the owner of the key can open it. It is used for encryption. A public key is like a public key. You can tell the people who need it. It is used for decryption.

In this process, a's private key is kept secret, a's public key can tell B, B's private key is kept secret, and B's public key can tell a. When a wants to send a message to B, a encrypts the message with B's public key. When B receives the message, B decrypts a's message with B's private key. None of the others who received the message could decrypt it. Only B owns the private key. In short, public key and private key exist in pairs in asymmetric encryption mechanism. Public key and private key can verify each other.

In the world of bitcoin, address can be understood as public key, and the process of signing and inputting password can be understood as the signature of private key. When each miner gets a transfer transaction, he can verify whether the public key and private key match. If they match, the deal is legal. In this way, as long as you keep your private key and know your bitcoin address and the bitcoin address of the other party, you can transfer bitcoin safely. There is no need for a centralized mechanism to verify whether the bitcoin sent by the other party is true.

Asymmetric encryption technology ensures the decentralization of bitcoin. Of course, distributed storage also ensures the decentralization of bitcoin._DJMINER

Why can't the blockchain ledger of bitcoin be tampered with?

The tampering here refers to the malicious modification of the account book in order to cheat in the network. This is guaranteed by bitcoin's workload proof mechanism and the longest chain mechanism.

Bitcoin's consensus mechanism is workload proof mechanism, which is an algorithm to reach a consensus on what happens in the same time and in the same order. The simple understanding of workload proof is a proof to confirm that you have done a certain amount of work, and the whole process of testing work is usually inefficient. It is a very efficient way to prove that you have completed a certain amount of work by authenticating the results of your work.

For example, graduation certificate and driving license in real life. By testing that you have completed a certain knowledge of learning, driving a certain degree of car to prove your skills. It turns out that you've done it before, and that you've spent so much time on it. The characteristic of workload proof is that the difficulty is moderate for the executing party. It's very easy for the validation party.

When miners do hash checking, it can be understood as a mathematical game. Getting the right answer will give you the right to book. After a very simple verification, other nodes can agree to keep accounts and synchronize their account books. After time stamping, they will rush to the next round of calculation competition._DJMINER

If someone wants to modify a transaction information in a block, what should he do?

From this blockchain, all blockchains are recalculated and the account books are synchronized to others. While he is doing the calculation, other miners have continued the calculation on the original blockchain.

Because in bitcoin's network, everyone thinks that the longest chain is the right one. So the malicious tamper needs to catch up with the height of the existing block in a very short time. Make your own blockchain the longest. Let other miners mistakenly think this is the right account book. Unless the person who maliciously tampers with it has great computing power. At least more than 50%, otherwise he would not have been able to make such a tampering.

At present, the computing power of the whole network is 800 million hashes per second, that is, 18 times 10 per second. At present, the popular mainstream mining machine in the market is about 10 tons of computing power. If you want to have 51% of the computing power of the whole network. At least 400000 of the latest mining machines are needed. If a mining machine is 10000 yuan, 4 billion yuan will be invested in the equipment. The production of the latest mining machine can't catch up with the sales, the buyer can't buy the spot, the old mining machine is constantly eliminated, and the computing power keeps rising, so the speed of the purchased equipment is hard to catch up with the rising speed of computing power. This investment needs at least 4 billion yuan. Without sufficient economic and technological strength, the average person will not attack.

From the perspective of network environment, due to the existence of decentralization, the whole network is very alert to this phenomenon. If the blockchain of bitcoin is tampered with, the price of bitcoin will be worthless. The profit obtained by tampering will also be greatly lost. Tampering with bitcoin's books is hard and unprofitable._DJMINER

Why can't bitcoin be forged?

How can you believe that the bitcoin I transferred to you is real or not fake, or that I transferred the bitcoin to you without transferring the bitcoin to two or three people at the same time?

Related to bitcoin's utxo organization, utxo means: transaction output not spent. A core concept of bitcoin transaction generation and verification.

For example: there are 20 yuan, 2 5 yuan notes, 1 10 yuan note, 2 5 yuan notes from the change given by the orange seller, and 1 10 yuan note from the change given by the candy seller. Take these three notes, I haven't spent them, so I can give them to you. This is the unused transaction output.

How did the orange boss get these two five yuan notes? It's from other people. The candy seller's 10 yuan banknote may also come from other people, so that the banknote can be traced back to the moment of initial issuance. Which printing company issued it according to the central bank's issuance approval, and which bank was first given the final circulation to the market. Thus, it is verified that all three notes are true, and the utxo of bitcoin is the same structure.

In the world of bitcoin, every transfer can be traced back to the original source, and every payment can be traced back to the previous collection. The bitcoin I give you must be given to me by someone else. The bitcoin that I haven't spent yet can be traced all the way back online to the block dug out by the miners when it was born. This mechanism ensures that bitcoin can not be forged or paid repeatedly.

Double payment is called "double flower". Before bitcoin, there was no perfect digital asset to solve the problem of Shuanghua. This mechanism solves the trust problem and makes bitcoin widely used._DJMINER

Combined with bitcoin's block time, under what circumstances can individuals make bitcoin "double flowers" successful?