No blockchain as safe as Bitcoin

Security is an essential characteristic for every blockchain. Satoshi Nakamoto, in the Bitcoin White Paper, explained that "the system is safe as honest nodes collectively control more processing power (CPU) than any group of cooperating attackers". In this sense, Bitcoin, by adding the highest processing power collectively controlled among all distributed accounting platforms, which increases the improbability of external or internal attacks, is emerging as the safest blockchain in the ecosystem.

The opposite, that attackers control a dangerous majority of the processing power in a chain of blocks, has materialized in different blockchain projects, which have been prey to attacks of 51% and block retention (for which it is necessary to concentrate about 30% of the processing power of the network). Recently, malicious miners attacked Bitcoin Gold, Verge and ZenCash, taking control of their networks and forcing other miners to double spend by imposing a chain of blocks that has been secretly mined to propagate, in such a way that a minibifurcation is created that invalidates previous transactions.

Meanwhile Bitcoin, the original blockchain and therefore the oldest one, has not been attacked under this type of modality, despite the fact that the condition for executing them has been given on different occasions. In the last 24 hours, three mining pools concentrate more than 50% of processing power (BTC.com with 23.4%, SlushPool with 14.8% and ViaBTC with 12.4%), of which only one of they are close to the percentage required for a block retention attack (BTC.com). However, attacking this blockchain does not seem so easy or viable.

Currently, the highest processing rate is that of Bitcoin, with a hashrate of 35,683 PH / s for June 9, which has been increasing rapidly during the last weeks. As can be seen in the following graph, although its behavior has been high and low, it has also been rare the occasion when some other blockchain has reached its processing power, although Bitcoin Cash did it at some point with the alternative migration of miners between both networks due to the temporary fluctuation in the value of the mining rewards in the early times of existence of this altcoin that arose from a Bitcoin bifurcation.

As seen in the previous graph, Bitcoin's processing power is much greater than that of other blockchains. Some of them also operate with the same SHA-256 mining algorithm or use the same ASIC hardware. Therefore, a miner who holds a fraction of the processing power in Bitcoin could take control of another blockchain that mines with SHA-256, and thus execute 51% attacks or block retention. This reality encourages attacking smaller blockchains instead of attacking Bitcoin.

For example, Bitcoin Cash at the same date, has a processing power of 4,779 PH / s, which represents 13.39% of the processing power of the network, a percentage that is almost doubled by just one pool of mining in Bitcoin, and to which other mining pools of the first block chain approach. On the other hand, blockchains of the likes of Litecoin and Ethereum have a processing power of 305.98 TH / s and 63.03 TH / s, respectively, values that are well below 1% of Bitcoin's processing power. Much lower is the rate of Bitcoin Gold processing, blockchain that was recently attacked, whose computational speed is 27.0987 MH / s, about 27 million hashes per second compared to the 35.683 quadrillion hashes per second of Bitcoin.

An external attack against Bitcoin is practically impossible to execute, since it would require approximately 2,300 million dollars between electricity and mining equipment, while in the smaller blockchains, these attacks would be cheaper. This is demonstrated by the list of Crypto51 costs to rent computing power in markets such as NiceHash to attack a blockchain for one hour.