Why does Bitcoin keep using SHA256 in its POW?

[cellard]

Another aspect to consider is the likely effect it would have on difficulty.  Along with the new algorithm, it would almost certainly involve having to implement emergency difficulty adjustments to the code so that blocks don't come to a temporary standstill when the hashrate suddenly plummets.  Also, since Bitcoin uses the total cumulative proof of work as part of its consensus mechanism, we should keep in mind the possibility it would make future contentious hardforks easier to pull off.  

Bitcoin currently attracts both the largest accumulated proof of work and the largest economic majority.  All the myriad forks we've witnessed so far haven't been able to keep pace with the proof of work Bitcoin has accumulated, but that wouldn't be the case if those who disagreed with the new algorithm continued to support using ASICs.  The new algo would almost inevitably be the minority chain in terms of hashpower, so supporters of the new algo would have to fall back on purely the "economic majority" argument and would also have to be pretty damn sure they'd win that argument.  Quite the gamble.

CPU mining might suffer from the same problems, and on top of that the network will be at the risk of attacks from botnets

And just to stress that point a little more...  Not exactly something we'd want to encourage in Bitcoin.

Yep, it would be similar to how when BCash forked they had to do some nasty trick with the estimated difficult arguments involving a series of forks... not cool for Bitcoin. An altcoin can pull that circus off but Bitcoin is too serious to go along with that.

Also the BCash side will for sure try to profit from the chaotic period to pump and probably deploy a spam attack while things are attempting to get solved).

Simply put, it's too late for Bitcoin to change PoW. We will need to see some kind of disaster that incentives global consensus to change it, and even then it will create conspiracy theories around the fact and there may not be global consensus even there.

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[ZmnSCPxj]

The obvious advantage of switching to ASIC resistant algorithms would be promoting decentralization as more people would be able to enter the mining process with "normal" hardware.

Again, what is the real sense of your meaning of decentralization? If you are talking about [more or less] fair coin distribution - just use (a kind of) random distribution. Otherwise, if there is any feasible way to increase one's part of [coin-]cake - one will always do so.

Wouldn't it be good for the stability of Bitcoin's network to have numerous small miners scattered throughout the world rather than a couple of big miners centralized in those parts of the world where electricity is cheap? Wasn't that the original idea back then in 2009? I believe so. But I also get the reality of this mining business and I know that what I'm asking is probably unrealistic. People with big money will always find a way to game the system.

I am emphasizing the above sentence "couple of big miners centralized in those parts of the world where electricity is cheap?"

I want to ask you this: if some parts of the world have cheap electricity, do you think big miners will not arise there if the best hash implementations are runnable only on wetware brains, CPU, GPUs, or FPGAs, but NOT ASICs?

The issue is not ASICs, but about cheap electricity.

[HeRetiK]

Wouldn't it be good for the stability of Bitcoin's network to have numerous small miners scattered throughout the world rather than a couple of big miners centralized in those parts of the world where electricity is cheap? Wasn't that the original idea back then in 2009? I believe so. But I also get the reality of this mining business and I know that what I'm asking is probably unrealistic. People with big money will always find a way to game the system.

I am emphasizing the above sentence "couple of big miners centralized in those parts of the world where electricity is cheap?"

I want to ask you this: if some parts of the world have cheap electricity, do you think big miners will not arise there if the best hash implementations are runnable only on wetware brains, CPU, GPUs, or FPGAs, but NOT ASICs?

The issue is not ASICs, but about cheap electricity.

Interesting argument, but the issue still lies with ASICs, in that the access to ASICs is rather restricted -- as opposed to consumer hardware such as GPUs and CPUs -- while ASICs producer also stand to gain money by simpling producing ASICs for themselves rather than the general public.

Cheap electricity leads to geographical hotspots, but the core of the problem is the centralization of power in a handful of companies, rather than territories. A multitude of companies from various nations all mining in China is less of a problem than a single company mining all over the world. Not that the first option would be optimal, mind you.

[etherixdevs]

Electricity consumption is an hard matter
Access to ASICs is restricted and not for the mass of peopl.
If we want to have real consumers to produce coins with their GPUs and CPUs, the road is not this one.

ASICs producer produce devices for their pockets, not convenient at all to  the general public.

Cheap electricity leads to geographical areas that have big probles of "regulations" and i do not know how serious they are.
The market and the goal of the white paper is too huge to leave it to under developed geographical regions of the world just for economic convenience.

Another problem is the centralization of power in the hands of few companies. Many companies from various nations, mining in China or Syberia is not a real problem. The core problem is a single company mining all over the world.

Implementation of new ideas is highly recommended.
I see equihash algo is generating new coins that are mineable from home GPUs and CPUs, creating real communities of real people.

[pereira4]

Electricity consumption is an hard matter
Access to ASICs is restricted and not for the mass of peopl.
If we want to have real consumers to produce coins with their GPUs and CPUs, the road is not this one.

ASICs producer produce devices for their pockets, not convenient at all to  the general public.

Cheap electricity leads to geographical areas that have big probles of "regulations" and i do not know how serious they are.
The market and the goal of the white paper is too huge to leave it to under developed geographical regions of the world just for economic convenience.

Another problem is the centralization of power in the hands of few companies. Many companies from various nations, mining in China or Syberia is not a real problem. The core problem is a single company mining all over the world.

Implementation of new ideas is highly recommended.
I see equihash algo is generating new coins that are mineable from home GPUs and CPUs, creating real communities of real people.

The problem is, if it can be mined with GPU's, it will sooner or later end up in specialized hardware for the task, no matter what algorithm you use, at the end of the day, it's just chips in a GPU, and they can be built upon an specialized machine that will be more efficient. GPU's are using resources for things unrelated to mining, so that power can be allocated to 100% mining in hardware.

Needless to say corporations could in any case stake massive amounts of GPU's rendering the average personal computer miner out of the game again.

[goddog]

ASIC chip to pow have to be cheap and easy to be produced, so more manufacturer can join the business at a relative low cost.
How many competitors we have producing GPU/CPU chips? thats centralization, also general purposed hardware can be resold, lowering attack costs. Datacenters miners will allways be cheaper than home miners and nothing can stop them to centralize.

Also coins mineable with GPU/CPU are often mined using maleware botnets, or stealing your workplace money so your network will be secured by evil, and thats not good. In any case honest home mining will be unprofitable y a waste of time.

Actual sha256 is great because it is very simple to produce asics to solve them.

Last days, I was thinking about how an emergency pow change can be done if something go wrong with actual double sha256 algo.

A pow change will definetly hit hard all mining industry, and I hope it will almost surely harm virtuos mininers harder than evil miners, so in the end evil will be prizewinner.

Thats a very hard problem to solve.
 think the only way to reduce damage can be, to change pow a little but not so much, so virtuos(but also evil) manufacturer can switch production easly.
In example, actual mining algo use double sha256, a solution to reduce manufacturer damage and to allow miners to get their mining hardware manufactured fast, and come back securing the blockchain ASAP, can be triple sha256.
this will make all previous hardware to be kicked out from the network, and will allow a fast substitution with new hardware.

but, this is a very ugly emergency solution it should not be used as some sort of antitrust to kill bitmain, as bitmain will come back stronger than ever. If you don't like bitmain you can support others manufacturer buying their hardware.
It is only an example, I don't think bitmain is evil, I think they are strong hard invested bitcoin believers. Some their actions can look evil, but they are only testing and provocating to make bitcoin stronger! Afterall bitcoin is an experiment !!!!