Quote from: AlexR12 on December 06, 2017, 04:11:27 AM

Hello!
I would really appreciate it if someone could clarify the following issue as I'm having hard times understanding how distributed ledger idea is actually implemented in Bitcoin. For simplicity assume that we have 10 miners (nodes in Bitcoin network). As far as I understand all of them have their own copy of the public ledger (right?) that is stored on their computers. Now assume that 1 miner gets 99% of the hash power and becomes dishonest in that he wants to change some of his past transactions. The question is: how is that possible (change past transactions) if he cannot access the ledgers of the other 9 miners? It seems to me that the dishonest miner can change only his own version of the ledger.
Thank you in advance!

You wouldn't be able to change the ledgers.

https://learncryptography.com/cryptocurrency/51-attack