DeutschTo understand what the 51% attack is, it is helpful to know what the Bitcoin infrastructure looks like. This consists of various elements, in particular:
- Miners
- User Interfaces
- Nodes
- Users with wallets
The Bitcoin network functions in particular via the nodes, which on the one hand manage transactions and on the other hand guarantee that they run on the basis of the basic rules. The miners, on the other hand, have the primary task of combining transactions into blocks and integrating them into the blockchain. The basis for the so-called 51 percent attack is now that potential attackers provide over 50 percent, i.e. at least 51 percent, of all miners.
How Does the 51% Attack Work?
First of all, the so-called 51 percent attack is absolutely not unrealistic, which is clearly demonstrated by the fact that the four largest mining pools alone generate more than 50 percent of all blocks together. If these mining pools were to join forces, it would be possible to always get their own blockchain through and thus carry out a 51% attack. This could, for example, involve feeding in incorrect blocks.
In practice, a 51% attack would probably look like attaching your own blocks to the blockchain. According to calculations, this is actually possible provided that at least 51 percent of the hash values are in the hands of a single attacker or a group of different attackers.
What Options Would Attackers Have in the 51% Attack?
In addition to the dangers explained above, there are other options that attackers would have in a 51% attack. Provided that there is actually control over the blockchain, attackers could also carry out so-called double spending transactions. This would mean that transactions are reversed and then transferred to another location. However, this would severely disrupt the Bitcoin mining system, as the attackers would also have the option of refusing to confirm transactions.
