Attacking Bitcoin with a supercomputer The difficulty in Bitcoin is recalculated every 14 days. What if immediately after this difficulty adjustment someone targets Bitcoin nodes with a supercomputer and start creating new blocks?

Such attack can create some many bitcoin to complete the series to the 21 million bitcoins before the 14 days pass by. Then the difficulty will be recalculated and it is going to result sky high, because of so many blocks were generated in the previous cycle.

But after that the super computer is disconnected, and the Bitcoin network (all nodes that were mining prior the attack) will have no power to create another block. The network will stall. The interest in mining Bitcoin will disappear and nobody would be able to withdraw anything, since you would need a supercomputer to create the next block, or wait for hundreds of years for the next block to come.

Is there any error in my reasoning? Is this scenario possible?
"TL;DR: Bitcoin mining is virtually immune to someone attacking it with a supercomputer, because the mining market is already flooded with supercomputers custom tailored to the job at the hardware level."
(via Cort Ammon in comments)



First of all, the difficulty reset happens after 2016 blocks. That's only after about 14 days if the hashrate is stable. When there is a steep increase in mining power the difficulty will therefore adjust much more quickly. The difficulty change is limited to a factor of four, so e.g. if the hashrate increased by a factor ten (at the start of a difficulty period), the difficulty would increase by a factor four after 1.4 days, and then again by a factor of 2.5 after 5.6 days, so that it would have adjusted a factor of 10 after only one week. Since the adjustment is an exponential function, the network can similarly adjust to even bigger jumps. You are correct however, that if the hashpower left at that point, the network could get stuck. 

Luckily, supercomputers are not effective at producing Bitcoin blocks. For Bitcoin blocks, the only operation that needs to be churned endlessly is a double SHA-256 hash. And that's exactly what Bitcoin ASIC miner hardware does, their chips have the necessary algorithm implemented in hardware and are therefore exclusively designed to calculate Bitcoin blocks. This is what makes even a single contemporary ASIC faster than thousands of computers.

The window for supercomputers to take over Bitcoin mining closed some time in 2012 or 2013. Today, the Bitcoin network produces about 10 exahashes/s. To my knowledge, the most cost effective miners come at about $100 per TH/s which translates to a magnitude of one billion USD invested in Bitcoin mining hardware alone.