Is a 51% attack on bitcoin likely?

Question

Given that the majority of bitcoin processing is done in China (source: https://bitcoinmagazine.com/articles/report-links-74-bitcoin-mining-china-sees-threat-network/), is it possible for a single entity to accomplish double spending (or be forced into accomplishing it by the Chinese government) to make profit for themselves or for the country?

How likely is it for all the separate entities doing the mining in China to be forced into complying and compromising the network's validity and has there ever been credible reports of such a thing occurring on bitcoin's front specifically?

Answer 1

No.

Bitcoin is an economical system. To become a pool operator, you must have 1) large amount of bitcoin or 2) large amount of hardware. Both requires you to be an "investor". In contrast to Proof of Stake, it is not easy to sell everything and leave Bitcoin in short time, which means you're informally "contracted" to Bitcoin. To put it another way, the only proper way to profit is long term mining. That requires you to ensure that it won't decrease in value. (1% increase is actually a lot for them) As a consequence, you can't attack Bitcoin even if you have the power to do that, as it'll affect its value.

This was the reason Emin Gün Sirer's Majority is Not Enough: Bitcoin Mining is Vulnerable was controversial.