Quote from: Bitcoinnation on December 23, 2018, 02:32:58 AM

I don't know whether am on the right board but I need some little help to grasp something.
I have been trying to read about the 51% attack but am having a hard time to understand the part where the attacker can "double spend the coins"

So in a layman's language
1. What is a 51% attack on the blockchain?
2. What would happen if someone managed to pull this off say on the bitcoin network?

Anybody well informed about this, I will appreciate your time and help.

I would like to add a couple of things that the fine gentlmen missed, which i think are very important and most average people don't know these.

The limitation of 51% attack

- the attacker has no way to use any coins that are stored in wallets they have no private key for. thus they are mainly limited to re-using aka " double spend" their own coins ONLY.

-The attacker can not make or create BTC out of no where except for what he they can mine.

- the attacker can not change the protocol rules, for example they can not say , okay block reward is every 10 seconds and block reward is 1000 btc.

- it is nearly impossible to perform such an attack in stealth-mode, every one and their grandmother would know if such an attack is launched on btc.

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if one understands the limitation as well the consequences of such an attack they will release that nobody who poses enough hashing power will even think of deploying such an attack, because that much power means a shit load of money invested, and as someone here mentioned that such an attack on BTC will sink it's value therefore taking the attacker to rekt city as all of their hashing power + whatever BTC they have will be worthless.