4 ms·
https://www.crypto51.app/ https://www.crypto51.app/ To execute a double spend, you the one sending the transaction and the miner must coordinate. For large tr
by crazypython 5y ago
https://www.crypto51.app/ https://www.crypto51.app/
To execute a double spend, you the one sending the transaction and the miner must coordinate.
For large transactions, it is recommended to wait for six confirmations. (six blocks that agree with the transaction and have not been 51%ed.)
The 1 hour 51% cost of Bitcoin is 1.9m$. However, you would need much more time than that to find six consecutive blocks alone, without the help of the network. So, while the network is 6 blocks ahead, you need to find 7 blocks. The network moves forward a block, you must move forward more than one block to catch up. This could take a long time, and longer the more confirmations required- each confirmation makes each previous transaction exponentially more secure. Simply controlling the mining power momentarily only puts recent transactions vulnerable.
However, that much hardware is available for rent-see “Nicehashable.”
- yuliyp 5y agoI don't see how more confirmations makes it exponenrially harder to mount a 51% attack: you just need to be mining faster privately than the remaining community until you (a) have a lead, and (b) have maintained that lead for the confirmation window.
- yanmaani 5y agoThere's luck involved too. In the limiting case, imagine you have 0.001% of the network hash rate and need a 1 block lead. This can happen every now and then, but getting a 2 block lead is basically impossible. The exact formula is given in the Bitcoin whitepaper <https://bitcoin.org/bitcoin.pdf https://bitcoin.org/bitcoin.pdf>, see page 6 and on.
- yuliyp 5y agoAccording to that formula, in a 51% attack, probability of success = 1 (since 51% attack means you are more likely to find a hash than all others combined), right?
- bellajbadr 5y agoThat's called Selfish mminign but the prob is to be faster than the network!