51% Attacks, how do they work?

Quote from Reddit (xx-08-2017): https://www.reddit.com/r/Monero/comments/6uhiix/question_how_do_you_perform_a_51_attack/?ref=share&ref_source=link

We always hear about 51% Attacks, but how are they performed? Here are the most important snippets from the discussion on reddit.


a) 51Pool finds a block and pockets it.
b) OtherPool finds a block
c) 51Pool finds another block and publishes them both, orphaning OtherPool
d) 51Pool is the only pool that can mine on the network.

Yes, you need to mine on top of the chain. You can’t mine on top of the block that you don’t know.

JollyMort about network rules:

That the 51% attacker can change rules is a misunderstanding. That’s also why running your own node is important. Your node would reject anything which ignores network rules, regardless of hashpower. The 51% must work within the rules, otherwise it would be a forked altcoin which nobody uses 🙂


Disclaimer: HJ does not encourage 51% or any other kind of attacks on cryptocurrencies. This is purely for educational purpose to improve the understanding of the technology.