Oleg Khovaiko, CTO of Emercoin, presented his algorithm for calculating the cost of a 51% attack on different blockchains. He introduced a numerically measurable hack51 coefficient, by which one can compare the potential resistance of cryptocurrencies to this type of attack.
The ratio of the attack cost to the capitalization of a particular cryptocurrency was chosen as the coefficient: hack51 = attack_cost / market_cap. The higher this coefficient, the safer the cryptocurrency in terms of the interest of attackers in carrying out a 51% attack, that is, the ability to collect enough computing resources to rewrite the block chain.
As the price of the attack, the cost of a daily cloud mining contract was taken from advertisements of companies that provide such services.. It then scales up to a hashing power equal to the current hash rate of the cryptocurrency network.. The weakness of this model is obvious, that is, the impossibility for the calculated price to collect the hashing power of more than half of the network to attack one or another cryptocurrency. Naturally, if you try to consolidate the corresponding hashing power, the price of contracts will increase many times. However, it is not supposed to study the practical stability of certain networks here, it is simply necessary to create a criterion so that their stability can somehow be assessed and compared.. That is, if someone wants to make a big commotion – he is quite capable of it.. It is very likely that someone could go short on a Bitcoin ETF and then compromise the network, dropping the price of the underlying asset to near zero.
Merged Minign (UNO) doesn't always help. The inaccessibility of mining in the absence of the unique properties of the coin does not attract miners, which reduces the complexity, and, as a result, increases vulnerability. Tech coins mined by co-mining (NMC, EMC) show higher resistance against 51% PoW attack. The fantastic resilience of EMC (an attack requires resources that are almost five times the capitalization of the coin) demonstrates the usefulness of Emercoin's triple consensus (PoS + PoW + MergedMining) to ensure the security of the blockchain.
Now everyone can run the above program for their favorite cryptocurrency and see the hack51 coefficient for it. Also, anyone can try to challenge the proposed stability criterion and try to find a bug in the program.