Suppose A transfers 10 bitcoins to B, but he wants to delete this information from the blockchain, so that everyone does not know that this matter exists, and can go wrong.
First, let’s talk about the longest chain principle. Assuming that there are two miners digging at the same time behind a certain block, or there are differences due to network delays, etc., at this time, each node first arbitrarily mines according to the block that it thinks is correct. Only when the next block is generated, there will be two chains at this time, but one is long. Bitcoin stipulates that the longest chain shall prevail. If a node is still stubborn to take the shorter chain as the criterion, he is fighting against most computing power. The result of this is that the blocks he digs are not recognized by everyone, which will waste time and computing power.
Going back to the above scenario, if A wants to renege on the account, he can only re-mining from the block before the block where the message of A->B10 bitcoins is recorded to create a branch chain, but the actual area The block has advanced a lot, he can only keep chasing, and while chasing, the main chain is also advancing, he must advance faster than the main chain, if his computing power is large enough, theoretically pass longer The time can indeed catch up with success, and the tampering of transaction information is realized. However, this is almost impossible, because no matter how large the computing power is, the average block generation speed is 10 minutes. From a non-technical point of view, if a person has more than half the computing power of the entire network, why is he not on the main chain? Continue mining? A person from a wealthy country might not be willing to be a thief.
to sum up
Blockchain is not the same as Bitcoin, and Bitcoin is not blockchain. Blockchain is just a technology applied by Bitcoin. This technology can inspire us. The greatness of Bitcoin lies in the application of unprecedented Blockchain technology. The application of blockchain technology still needs to be explored.
Bitcoin is the most successful application of blockchain technology, but Bitcoin itself has many problems. It wants to challenge sovereign currency by issuing currency. This motivation is open to question. In addition, due to the anonymity of Bitcoin, only a public key or address is required to conduct transactions, which provides a good platform for the black industry. In addition, Bitcoin is not a mature payment system. It has shortcomings such as low throughput and poor scalability.
Maybe the text is still pale. You can watch the video explained by Teacher Li Yongle. Although it is not detailed, it is easy to understand.