On: Show HN: Cost of a 51% Attack on Popular Cryptocur...

[std_throwaway]

OK, so by 51% you really mean at least 50%. Do you happen to have a background in finance? It's quite unusual to say 51% in math/engineering.

[paulgb → std_throwaway]

"51% attack" is the name of the attack, but you don't actually need 51% of the hash-rate to do it, just 50% plus a small margin.

[direction534 → paulgb]

You dont need 50%. You can do it on 1% with luck.

[std_throwaway → direction534]

Is there a known probability curve?

With so many actors it could be very steep. Like 51% capacity has 99% chance of success and 49% has 1% of success and 40% has practically zero chance (these are made up numbers).

It could also be quite shallow as in 1% capacity gives you 1% of success... that would actually be quite bad and invite malicious actors to test the system with regular attacks.

[im3w1l → std_throwaway]

It's a race of who can get to N blocks first. The higher N the "steeper" it is. N is set by the merchant so as to balance security with quick transactions

[CryptoPunk → std_throwaway]

"51% attack" is a term of art in the blockchain field.

[std_throwaway → CryptoPunk]

I see, the number in the name is not to be taken too literally.