Читать книгу Cryptocurrency Mining For Dummies - Peter Kent - Страница 23
Blockchain is “immutable”
ОглавлениеYou may have heard that the blockchain is virtually immutable, which simply means that it can’t easily be changed. If the Bitcoin blockchain says you own x Bitcoin, then you do own x Bitcoin, and there can be no disagreement … and nobody can go into the blockchain and hack it or somehow change or mutate it.
Imagine what would happen if someone went into a block (we’ll call it Block A) and changed a little bit of data — for example, they go in and show that instead of sending someone 1 Bitcoin you sent 9 Bitcoin.
Well, the hash in Block A would no longer match its data. Remember, a hash is a fingerprint that identifies the data, so if you change the data, the hash no longer matches.
Okay, so the hacker could rehash Block A’s data and then save the “corrected” hash. But wait, now the next block (Block B) would not match because Block B is carrying Block A’s hash. So now say the hacker changes the Block A hash stored in Block B.
But now Block B’s hash doesn’t match Block B’s data, because that hash was created from a combination of Block B’s transaction data and Block A’s hash!
So, Block B would have to be re-hashed, and the hash updated. But wait! That means Block B’s hash stored in Block C now doesn’t match!
See where we’re going? This would ripple through the entire blockchain. The entire blockchain is now broken, by just modifying one single character in a block lower down. In order to fix the problem, the entire blockchain has to be recalculated. From the hacked block onwards, it must be “re-mined.” What may look like a simple hack and database edit now turns into a major computational headache that cannot be easily completed.
So, this hashing function, combined with the fact that thousands of other nodes must be in sync with identical copies of the blockchain, makes the blockchain virtually immutable; it simply can’t be easily hacked.
Nobody can change it or destroy it. Hackers can’t get into the peer-to-peer node network and create transactions in order to steal crypto, governments can’t close it down (China, for example, could attempt to shut down Bitcoin within its borders, but the blockchain would continue to exist in many other countries), a terrorist group can’t destroy it, one nation can’t attack another and destroy its blockchain, and so on. Because there are so many copies of the blockchain, and as long as enough people want to continue working with the blockchain, it’s practically immutable and indestructible.