What can’t be hacked, please?
Bitcoin has (roughly) two attack vectors, the blockchain itself and the bitcoin transfer.
Bitcoin is just a collection of characters.They are not transferred in a personalized manner. The one who has the key has the Bitcoin. You can illegally acquire Bitcoin by attacking an exchange, some of which are surprisingly poorly secured, or by attacking computers on which Bitcoin is stored and appropriating the corresponding keys.
But you can also try to attack the blockchain itself by a so-called 51 percent attack.The Bitcoin offshoot, Bitcoin Gold, was caught by this.
In a 51 percent attack, an attacker considers more than 50% of the computing power to be a blockchain.This can then be used for various manipulations.
A blockchain consists of blocks that are calculated.A new block is added when someone has performed the required calculations. It depends on the time, who comes first, paints first. If two blocks are calculated at the same time, a turn-off occurs. Then you can calculate blocks for both branches. The branch that “wins” that gets longer. The transactions in the then orphaned branch expire as if they had never taken place. If someone now has a majority of computing power, they could use it for so-called double expenditures. You make a transaction. This is entered in a block. Then you use your computing power to calculate an alternative continuation of the blockchain. in this sequel, you move the coins that you have just moved somewhere else (or not at all). Since you have the majority of the computing power, you can calculate this continuation faster than the rest of the participants. If you publish your longer branch, the other dies. Specifically, you transfer an amount of coins to an exchange and receive money. After receipt of payment, the alternative branch is published. You still have the money. But by deleting the stock exchange transfer, you also have the coins. The stock exchange can, of course, try to reclaim that money.
You can protect yourself from implementing a blockchain in such a way that it becomes difficult to impossible to achieve 51% of computing power.As a stock exchange, you can protect yourself from it by waiting longer until you actually accept transactions as completed.
The problem (in my opinion) is not necessarily that something can be hacked.Everything can be hacked, including your bank account. The problem is that you don’t have legal safeguards. If someone hacks my bank account, I can still contact my bank with replacement claims. If someone goes shopping with my credit card details, I also have ways to get my money back. This hedge is (still) completely missing for cryptocurrencies. Appropriately, you should handle them carefully.