
Proofs of Useful Work [pdf] - pmuk
https://eprint.iacr.org/2017/203.pdf
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Taek
Useful work is not actually a good foundation for securing a decentralized
cryptocurrency.

The value of PoW in cryptocurrency is that I know for a fact that you have to
burn $X million dollars if you want to double-spend my cryptocurrency. That
has to be burned in electricity, and that burn can't be used for anything
else. It's expensive for you to attack me.

If suddenly we've got useful works, such that you can apply that $X million in
electricity to solve problems that are actually not wasteful, and worth
perhaps $X million dollars in solutions, then I don't actually have confidence
that it costs you money to double-spend my transaction. You might be able to
double-spend my transaction as a by-product of computation that you were going
to do already.

Further, useful PoW is a centralizing pressure, because not everyone is going
to have equal access to people who are willing to pay for solutions of useful
work. This unequal access to revenue means unequal ability to compete,
favoring people who are able to sell solutions more effectively. For
cryptocurrency, we like to remove these advantages as much as possible
(granted, the existing system has a lot of room for improvement, but useful
work moves things in the wrong direction).

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voidmain
The ideal would be useful work that is a public good - no one can profit from
it individually (other than by using it as a PoW), but the world benefits from
it in some way.

~~~
richdougherty
That's a really interesting thought. Would you consider public information
(e.g. the result of a mining computation) to already be a public good?

E.g. see discussion of information goods here
[https://en.wikipedia.org/wiki/Public_good#Challenges_in_iden...](https://en.wikipedia.org/wiki/Public_good#Challenges_in_identifying_public_goods)

~~~
0wing
Satoshi style PoW algorithms are intended to waste as much energy as possible.

PoW mining just raises the capital cost to control the network without ever
improving the speed or functionality. It's a system that increases the waste
as time progresses.

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etaioinshrdlu
Here's a little writeup of how I could imagine mathematical proofs as a useful
proof-of-work:
[https://pastebin.com/raw/ZAys0mYp](https://pastebin.com/raw/ZAys0mYp)

Note that it's more of a market for mathematical proofs, not a replacement for
proof of work in a currency that needs a new block every 10 minutes.

Still, "miners" (theorem provers) get rewarded for their efforts with tokens.

My mathematician friends say such a genericized proof market should be
possible using Model Theory.

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tromp
This work is theoretically very interesting, but nowhere does the paper
explore what parameter choices would make its use in e.g. bitcoin practical.
In particular, would n be close to a million? How large would the problems
(f,x) be? How large are the solutions? Both of these would need to be included
in the block header which is currently only 80 bytes long. Any sizes
substantially larger than a few KB would make this rather impractical. What
are the best known implementations for these sizes? How many seconds does it
take to solve and how many to verify a solution?

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jcoffland
An important consideration that is missing in section _7 A Blockchain Scheme_
is that the PoW must also be tied to the miner's receive address otherwise
anyone could claim the reward as soon as the PoW was broadcast onto the
network. A simple solution is to also hash the miner's receive address along
with the previous block and transaction hash. This seems like a pretty major
omission on the part of the authors and cast some doubt on the rest of the
paper.

~~~
tromp
It's not so much missing, as it is implicit in the H(current block), since
current block includes all transactions, includes the coinbase for the miner.
(In reality, only the merkle root of the transaction tree is hashed, with
similar effect).

~~~
jcoffland
Right, my mistake.

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kruhft
There's a better way using an obscure Coin algorithm.

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thruflo22
I love it when a plan comes together.

[https://news.ycombinator.com/item?id=14949971](https://news.ycombinator.com/item?id=14949971)

