James, sorry for not understanding you in what you exactly had in mind. Got it.
And i agree absolutly in your first point here that smaller coins on an algo, no matter if Asic or GPU, are more at risk of a 51%, just logical.
But i argue with your 2nd point from a logical point of view, unbiased, seriously!
While in theory it could be done to build up hashing power for a 51% attack i don’t think this would be neither the smartest way nor the best, nor the fastest.
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To build up an asic farm for the purpose of an 51% attack on an at least medium coin.(let’s say marketcap <#50) would be extremly expensive.
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Such farm would be limited to the coins on the algo, ok, on sha256, X11 and scrypt there are enough coins someone could attack, but than again, the hashpower is so big there that it’s nearly impossible to get the hashpower together on the top coins enough for a 51% attack.
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On other algos, like equihash, it just wouldn’t make sense, with a handfull coins on a given algo to invest that much money for an 51% purpose. Every attacked coin could make an “emergency fork” for example, rent temporary hashpower and for sure their are some counter measures that can be taken. After such attack what would the attacker do with his farm? Just nothing …
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My perosnal opinion is that the easiest way performing a 51% attack is renting GPU hashpower. No hardware investement, no follow up costs, no maintain costs, no shipping, no installation, no room, no nothing. Pay and get whatever hashrate you need that can be directed just everywhere and is not limited to any algo at all. Actually i’am pretty sure that most attacks are done exactly like this, and that for exactly these reasons.
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You could such asic attack forseen mostly. Let’s say the private bitmain pool that has below <10% right now has 75%, than of course everybody would be well aware that there is indeed danger and the given coin is at risk. The Asics that are on an algo are just there, while someone with bad intention could shift around gpu hashpower however he likes, rent and shift it to wherever you want.
This is just my own logical opinion of course.
Just saw you added something to your comment while i reply.
I can see the math that 50k Z9’s would be cheaper than 700.000 GPUS. Didn’t check how much would be needed for a 51% attack so i take your numbers as they are.
The point is that nobody would buy the GPU’s but just rent them for some hours. Pretty sure that would be way cheaper than 50.000 Asics, it’s building, power instalation, personal that you can throw away later if the target is gone as this would be happen. IF zcash would be attacked, some others fork away you literally can throw away 50.000 Asics, doesn’t make much sense to me, seriously.
In theory i see the possibility, in practice the chance is about zero, the asic would suicide itself on that algo.
For me the biggest danger for a 51% attack was since ever gpu cloud mining and mining rental services.
