Bitcoin Forum

We're looking at alternative ways to structure our POW and considering whether something like a reCAPTCHA mechanism could be used.  Obviously a user-centered and visual mechanism wouldn't fit, but something where the work involved generates some reasonable outcome.

Have others considered this on the forum?  We're not finding much literature on implementing other POW for bitcoin networks.

Our current algorithm requires communication to other servers outside of the bitcoin network.  I suspect that completely kills it, but I would be curious about others opinions.

One interesting project in this direction was Motocoin - there, the PoW consisted of finding a solution to a "puzzle" game.  (But in the end, humans were overtaken by bots.)

The idea is solid, a human powered PoW has merit from a technical and curiosity standpoint, the real trick is making it secure against bots. Google recaptcha is constantly being updated by google's engineers to counteract the ever changing bot landscape, which is something a blockchain cannot really do.

You'd need something more intelligent than a captcha to solve which bots wouldn't be able to attempt.

As the current state of science, it's rather a philosophical problem.

Design a PoW function that only a human can solve, but a machine can (easily and accurately) verify for corectness.

When you do this, you will be a new Satoshi :)

The proof of work concept is already a form of reCaptcha so why are we even contemplating this.The proof of work in Bitcoin network is already harder than reCaptcha so why should we mimic a proprietary concept to build a new crypto or hard fork.

The thing is, do we want this?

Decentralization is only one aspect of crypto-currencies. Automation is arguably another.

Isn't it one of the positive side-effects of crypto-currencies and smart contracts, that you could potentially handle all sorts of transactions and contracts without any human intervention at all? Wouldn't it be kinda cynical to cut humans out of the arbitration and confirmation process, only to put them to work as what would basically be a human captcha-solver?

What I was really trying to get at is the re-harnessing of the PoW compute power to solve an interesting problem.  Still with the idea of leaving humans out of the loop -- so not involving humans as screeners, but using the PoW concept to address ongoing problems that are controlled via API calls to/from other computers.

The compute problem could most certainly be distributed, so its not a central/single API server.  But, the certification of the blocks would not then be simply a race without a compute meaning, it would imply that each mining event is helping to solve a problem.

I'd suggest the problem be a computation related to science, and we have some candidates in mind, but it doesn't have to be a particular domain of knowledge, just something better than a wasted set of CPU cycles.  It was for that reason that I titled it with the reCAPTCHA idea, but maybe it was misleading.  I do agree that the current PoW is similar to reCAPTCHA, as a check on validity, but I would argue that its not like reCAPTCHA in that the computation is not harvested to help with some other problem that needs a solution (e.g. book translation or image ML).

Ah, got it. There have been a couple of alts that are (were?) trying to go this route. Two which I remember are Primecoin and FoldingCoin. I'm sure there are other examples.

One of the problems to be aware of is that the PoW that gets put into eg. the Bitcoin blockchain is not wasted, it is used to secure the transactions. Using said computing power for other means always comes at the cost of security, ie. cycles that get used for research can't be used to secure the network and vice versa. However there might be recent research that tells us otherwise. Maybe the aforementioned alts can serve as a starting point.

I don't know what you want - can only speak for myself.

A relation of one human being = one unit of hashing power, would certainly be an important property of a block chain based currency that is supposed to be controlled (owned) by the people. One that is supposed to benefit the people by enabling every single individual to equally participate in the creation of the value.

However, we're currently living in times where crypto-currency "experts" keep claiming that hashing power does no mean shit for the value of the currency. So it is certainly not a popular way of thinking nowadays.

But personally I believe that inventing a PoW function that can only be solved by a human brain would be the optimal ultimate solution. At least from the social point of view.

Yes, that would be a big deal - essentially proving that the Turing test can’t be satisfied, while allowing a machine to prove that it can’t be satisfied.