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51% Attacks on Crypto Becoming More Expensive Again (Not For Everyone)

Sead Fadilpašić
Last updated: | 5 min read

A so-called 51% attack, in which a villain gains control over the majority of the computing power on a cryptocurrency network, is a real threat in many smaller networks that rely on the Proof of Work (PoW) consensus algorithm. Now, along with the new market rally, the theoretical costs of going through with an attack like that have increased – but not for everyone, as some coins are now in even more danger of being attacked.

Source: iStock/NiseriN

Compared to December last year, when the cost for such an attack dropped significantly after the mid-November market crash, the networks seem to be strengthening their positions – some almost tripling the amount of money you’d need to fork out to really do it any harm.

“The thing to keep in mind is that 51% attacks, while they’re terrible and undermine confidence, basically just allow double spending. This is really bad for merchants and exchanges <…> But it doesn’t allow the attacker to, say, steal everyone’s coins. And the cost of a rollback goes up as you go farther back in time,” Prof. Matthew Green of John Hopkins University recently told

Here’s how the theoretical costs* of one hour attack has changed for some of the Proof of Work coins.

Bitcoin Cash: +182.7%

The 51% attack cost: December 2018: USD 7,896 / April 2019: USD 22,322
BCH price change this year: +94%
Market capitalization: USD 5.6 billion

Bitcoin Cash marked the largest improvement in cost among major coins since December 2018, when it was recovering from the hard fork that led to the birth of Bitcoin SV.

Litecoin: +175.55%

December 2018: USD 18,203 / April 2019: USD 50,159
LTC price change this year: +157%
Market capitalization: USD 4.9 billion

Litecoin joins the list of almost tripling the cost of an attack after its price more than doubled this year.

Ethereum Classic: +57.6%

December 2018: USD 4,008 / April 2019: USD 6,317
ETC price change this year: +20%
Market capitalization: USD 686 million

Ethereum Classic is an example of how percentages can be misleading: even though the cost significantly increased, NiceHash, a Slovenian cryptocurrency cloud mining marketplace, can offer 72% of the needed hashing power for the attack. Moreover, in January of this year, ETC suffered a 51% attack that resulted in a deep chain reorganization which included a double spend of ETC 219,500 (USD 1 million, at the time) in total, even when the necessary hashing power would have cost USD 7,939 – even more than today.

Metaverse ETP: +50.89%

December 2018: USD 224 / April 2019: USD 338
ETP price change this year: +4.56%
Market capitalization: USD 44 million

Serving as yet another example of misleading percentages, the amount currently needed could even be considered pocket change to some, especially considering that an incredible 1,338% of the hashing power is available for rent on NiceHash. The team realizes this possibility, having announced in January that they’re moving away from the PoW consensus algorithm in favor of a hybrid one called “Pillars of Creation.”

Bitcoin: +36.24%

December 2018: USD 275,613 / April 2019: USD 375,502
BTC price change this year: +38%
Market capitalization: USD 93 billion

Bitcoin’s percentage may be called misleading as well, since it has not risen as much as the previous coins on our list, but the cost is certainly prohibitive and it’s not clear whether someone could offer enough hashing power for rent.

Zcash: +25.33%

December 2018: USD 15,228 / April 2019: USD 19,083
ZEC price change this year: +20%
Market capitalization: USD 441 million

Privacy coin Zcash also seems to sit comfortably in relative safety as NiceHash only offers 6% of the hashing power, but many are pointing out that its algorithm called Equihash has already been the victim of one such attack back in June 2018, when more than USD 550,000 was double spent from ZenCash at a cost of around USD 30,000.

Ethereum: +24.83%

December 2018: USD 75,390 / April 2019: USD 94,112
ETH price change this year: +23%
Market capitalization: USD 18 billion

Ethereum is yet another network protected by the size of its network like Bitcoin, as participating nodes are not clustered closely enough to let malicious actors seize control of them – which also happens to be the point of decentralization.

Dash: +15.81%

December 2018: USD 3,851 / April 2019: USD 4,460
DASH price change this year: +53%
Market capitalization: USD 1 billion

As it was suggested back in January, in case of Dash, a single miner held a significant portion of the hashing power – whereas more than half of it was held by this very same NiceHash. However, the team has announced a solution called ChainLocks to even eliminate this threat.

Bytecoin: -38.73%

December 2018: USD 315 / April 2019: USD 193
BCN price change this year: +30%
Market capitalization: USD 169 million

Bytecoin decided to go the other way since December. Not only is it incredibly cheap to attack the network, but NiceHash also offers 46% of the hashing power an attacker would need. However, whenever this point was raised with the team, they dismissed the possibility, once even writing in a Reddit post, “Basically the price quoted in the article […] is accurate, but as soon as a user or users start to purchase this hash power the price, according to economic rules, begins to rise astronomically. It could be 200-1000 times higher than the price they have listed there and that is only of course, if the hash rate is there to buy in the first place.”

Electroneum: -50.46%

December 2018: USD 2,364 / April 2019: USD 1,171
ETN price change this year: -34%
Market capitalization: USD 49 million

And while Electroneum is not as cheap to attack as Bytecoin, it also shows a worrying trend of halving the price necessary for this. It has also been the victim of such an attack mid-2018, and it was proven several times that there are mining pools making up a worrying amount of hashing power.

Bitcoin Private: -80.85%

December 2018: USD 47 / April 2019: USD 9
BTCP price change this year: -71%
Market capitalization: USD 2.3 million

Bitcoin Private is one of those coins where the calculations go far beyond theoretical territory. NiceHash offers 12,365% of the hash power you need for merely USD 9. Additionally, in October last year, an ethical hacker under the nickname Geocold livestreamed his 51% attack on this coin to prove how easy it could be.

* – calculations are based on the previous report by and information provided by a website called which tracks costs of these attacks and calculates how much of hashing power an attacker might rent from NiceHash, a Slovenian cryptocurrency cloud mining marketplace, to match the current network hashing power for an hour.