Bitcoin security is due to the transaction validation protocol that sets its code; and although the miners play an important role in this process, they are not the only ones involved.
The validation of transactions in Bitcoin is done through the consensus of the nodes. These are the popular accounting books where everything is registered.
In the Bitcoin blockchain, there is no central node; Thus, all participants in the network have a copy of the accounting book, and they are responsible for attaching a new transaction, if the consensus says that it is correct.
In this way, those that are not validated are discarded, creating unsupported bifurcations; Meanwhile, the main network is the longest chain, the one with 51% approval.
But what would happen if this 51% is controlled by a person or group? Would Bitcoin security be at stake? In theory, yes, although it is practically impossible; Then we tell you why.
What does it take to violate the security of Bitcoin?
The recipe to do it is really simple, the question is the complexity of the ingredients.
To corrupt the security of Bitcoin you need: 51% of the nodes and a mining network strong enough to validate all the blocks while the attack is taking place.
Currently, according to Bitnodes data, there are 11,055 nodes distributed around the world, so it is necessary to have control of more than 5,500 nodes to perform this attack.
How much does it cost to attack Bitcoin?
According to the blockchain data source, Messari, attacking the Bitcoin network today costs USD 21 million, to cover the electricity costs of an attack for a whole day, having prior control of 51% of the nodes.
This attack is able to block real transactions, reverse recent transactions and reorganize the confirmed blocks to generate double spending; This last situation would be quickly detected by the network, and to correct it, they generate a fork that leaves out the reorganized blocks.
An Ethereum security attack is 8 times cheaper than BTC, exactly, USD 2.7 million is needed to attack this network.
In the case of BCH, BSV and Bitcoin, less than USD 1 million is required to attack any of those chains.
The security of the Bitcoin Gold, Vertcoin and Verge blockchains have been the most relevant victims of the 51% attack, due to the small hashrate force their chains possessed at the time of the event.
In the case of Bitcoin, getting control of the sufficient percentage of the total hashrate rate is really difficult; Not counting, how fast the actions should be performed, so that the wrong transactions are validated without first being identified by honest nodes. Most likely, this attempt to steal money will result in losses for criminals.