Bitcoin does not derive its value from mining hashpower. Bitcoins value incentivizes and indeed, pays for hashpower. As codewench says, if all the ASIC miners started churning out invalid blocks, Bitcoin could proceed with an old Celeronbut of course that would not happen, because miners want to make money.
This has always struck me as possibly the biggest realistic attack vector for the network, the lack of emergency difficulty adjustment. The Celeron would work great, provided you get through 2016 or so blocks, but depending on how much hashpower you've lost, that could take a prohibitively long time? Is the solution here pretty much "we can hardfork if the time ever comes"
Wherefore ideas such as
Malice Reactive Proof of Work Additions (MR POWA) (
blogged,
reblogged,
discussed on this forumtheymos immediately pointed out one obvious problem). I do not endorse that proposal; I think its interesting, but I have no desire to see collateral damage made of all the fine folks who invested their lives savings in SHA-256 hardware, and swore they would mine Bitcoin or nothing.
Thus far, Bitcoin has successfully stared down threats and active attempts to cause exactly what you describe. Anti-Core/anti-Segwit/pro-BCH/2X/whatever watering holes have been perpetually filled with talk of the flippening and killing off the legacy chain (
i.e. Bitcoin), amidst much bravado. At one point just last month, there was a serious contest of hashpower accompanied by market manipulations which pumped-and-dumped BCH, whilst knocking down Bitcoin down 30% for all of a few days. This was timed carefully, so that the desertion of malicious miners would hit right after a 2016th-block difficulty adjustment. Bitcoin got kind of slow, as its hashpower plummeted; BCH supporters were jeering that Bitcoin would grind to a halt, predicting that hashpower would drop low enough that it would take months to reach the next difficulty adjustment.
That situation lasted for approximately 48 hours, until miners flocked back to where they could make the biggest profits. The end of that battle was that Bitcoins hashpower stabilized, little guys who threw their money into BCH at its peak got wiped outand Bitcoins exchange rate rebounded to a new all-time high within a week or so, thus giving miners all the more reason to stay with Bitcoin!
The more often Bitcoin faces such attacks, the worse it crushes its attackers; and thus, the more of a reputation it gains for being anti-fragile and a honey badger (or money badger). From a public relations perspective, attempts at flippening away Bitcoin by draining its hashpower have made those who try such things look ridiculous.
The war isnt over, of course; and I myself am worried about miner centralization as a matter of principle. It is most worrisome that the worlds biggest vendor of SHA-256 ASICs is actively pro-BCH/anti-Bitcoin, and currently accepting payment in BCH instead of Bitcoin. I want to see commodity SHA-256 ASICs sold cheaper than GPUs, and as readily available. I think thats probably the best solution, long-term. Too bad I am not a hardware guy.