So, the attacker has X% of the hashrate. The attacker is attempting to mine 16 blocks within the time that the trustworthy miners mine at most 15 blocks, as a result of e.g. the sufferer waits for 15 confirmations on transactions of the attacker’s deposit quantity. If the trustworthy miners get fewer than fifteen blocks, the attacker nonetheless wins on the sixteenth, they’ll simply await the fifteenth block (and even assist mine it, so as to add to their alibi).
Kindly, Satoshi Nakamoto left us a components that addresses precisely this state of affairs within the whitepaper on web page seven:
Supply: Bitcoin Whitepaper
Even with a hashrate of 30%, the possibility of success for such reorganization lengths is fairly low. Satoshi calculated additional:
q=0.3
z=0 P=1.0000000
z=5 P=0.1773523
z=10 P=0.0416605
z=15 P=0.0101008
z=20 P=0.0024804
Which provides one % probability of success with thirty % hashrate to displace 15 blocks.
Clearly, the possibility can be greater if the attacker might leverage greater than 30%, however even 30% appear pretty unlikely, on condition that this may require not less than two, extra possible three of the most important hashrate suppliers to make themselves accessible for such an assault, or much more of the smaller ones.
by way of miningpoolstats.stream/bitcoin
Additional, normal computing energy is ineffective, since Bitcoin makes use of specialised {hardware}, and there may be hardly any SHA-256 hashrate rentable. Crypto51, a web site devoted to monitoring the price of a majority assault for varied networks, estimates {that a} majority assault on Bitcoin would value about $1.2 M per hour on the going fee for hashpower, however the rentable SHA-256 hashrate by way of Nicehash solely quantities 34% of BCH’s hashrate, which itself is a fraction of 1% of Bitcoin’s hashrate.
by way of crypto51.app
So, except the attacker manages to take management of a number of current mining swimming pools for a number of hours, this does not actually appear significantly possible.