5 ms·

I'm curious, if you owned 51% of the network what's to stop you from rebuilding the entire history of the chain and then adding new transactions (including any

• aordano 4y ago
  Nothing, that's called a hard fork. It has happened (out of consensus) and probably will happen again.
• Kranar 4y ago
  Nothing, mcintyre1994 is simply wrong about this. You don't need 51% to block transactions, any miner who completes the proof of work can legitimately block a transaction and Bitcoin went long periods of time where various miners blocked transactions and just took the mining reward. As for deleting, unless you want to enter a philosophical argument on the nature of deleting, and whether anything in the universe can truly be deleted [1], for all practical purposes a 51% attack does allow one to delete transactions off the blockchain but the older the transaction is the more expensive and impractical it would be to do so. A 51% attack does not allow someone to create new bitcoins or spend coins they don't have the keys to, but they could double spend coins or delete existing transactions. [1] https://en.wikipedia.org/wiki/No-hiding_theorem https://en.wikipedia.org/wiki/No-hiding_theorem