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The bitcoin network, including every miner, is the biggest computing project that humanity has created. Thus I ask: why, instead of using it to generate useless data, don't we use it to generate meaningful data, such as theorem proofs or something similar to folding@home?

marked as duplicate by Nick ODell Apr 22 '15 at 8:04

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    Your question is based on the assumption that securing the Bitcoin block chain is useless. – David Schwartz Jan 21 '14 at 4:16
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    @DavidSchwartz and other readers who understand the same: that is not what I mean. I said that the problem used itself is not useful (solving hashes). I'm asking if we could use other problem that is useful for other purposes (ie, protein folding) while still being able to maintain the blockchain security as well as the current approach. – Dokkat Jan 21 '14 at 4:26
  • See my answer. Protein folding has nothing to do with Bitcoin mining. – David Schwartz Jan 21 '14 at 4:31
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    Gridcoin and Curecoin are doing this. CureCoins can be earned by running 'Folding @ Home' and mined by SHA-256 mining. Gridcoins can be mined by mining Scrypt and you get a 'bonus' when running BOINC. – Mr Jones Apr 22 '15 at 8:27
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Solving SHA256 hash problems on Bitcoin is useful in the sense that secures the Bitcoin blockchain, but if your question is: "why can't it do something computationally useful as a side-effect?", then I think the answer is "we don't know how". For Bitcoin to work, the proof-of-work that miners do must have the following properties:

  • Easy to verify solutions

  • Hard to find solutions

  • Difficulty of finding solutions can be precisely quantified

  • Provably inseparable from the block it secures

Cryptographic hash functions like SHA256 satisfy these four properties. I don't think automated theorem proving fits the bill because, as far as I'm aware, there is no way to prove how difficult it was to find the theorem that you proved. General purpose grid computing, like BOINC, doesn't fit the easy-to-verify requirement, at least in the context of Bitcoin. (In fact, I think this is an active area of research in grid computing, called the "cheating problem".)

If there some proof-of-work scheme that satisfies these four properties and also has some useful computation as a side-effect, that would be interesting. I'm not aware of any.

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    You missed the most important requirement -- the work must be provably inseparable from the block it secures. Otherwise, it fails to secure the block. – David Schwartz Jan 21 '14 at 9:47
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    Quite right @DavidSchwartz, amended my answer. – paralogical Jan 25 '14 at 15:03
  • @dokkat Properties 1 & 2 are the reason why a circuit-optimizing proof-of-work would be of no use: it'd take exactly the same effort to find an answer than to verify it. Too bad, for it'd be a really useful task, which could also satisfy #3 (not sure on #4). Folding proteins has the same problems, plus doesn't satisfy #4. Analyzing SETI data satisfies 1 & 2, could satisfy #4 by linking it to a timestamp, but then you'd lose the network decentralization (you'd depend on accurate handling of data by SETI). Etcetera... – Joe Pineda Feb 12 '14 at 13:23
  • Now that I think of it, a proof-of-work that generated random pieces of music in MIDI format so the hash (any hash, even MD5) of the mini-file attached as stub to the block satisfies the difficulty requirements could count as "useful" in the eyes (or should it be "ears"?) of people who find such random, computer generated music pieces as "pieces of art". You could even require the length to increase with the difficulty, or establish such pieces should satisfy the rules of, e.g. Baroque counterpoint. Most pieces would be garbage, but occassionally beauty would emerge :) – Joe Pineda Feb 12 '14 at 13:30
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Well, I know of one altcoin that does useful work: Primecoin.

As Wikipedia describes it:

Primecoin (sign: Ψ; code: XPM) is a peer-to-peer open source cryptocurrency that implements a scientific computing proof-of-work system. Primecoin's proof-of-work system searches for chains of prime numbers.

Primecoin already has quite some world-record prime chains on it's name: some Cunningham chains and some Bi-twin chains.

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    Finding cunningham chain records may be satisfying for those who found them, but it's not useful in any way. Chains used in applications don't need to be record-breaking any more than prime numbers need to be record-breaking. – Meni Rosenfeld Feb 12 '14 at 8:07
  • There's already a Primecoin clone, by the way - should it fail, are the chains discovered on that network dissappearing? Hope not. Likewise, when a block goes orphaned on Primecoin, all the effort in discovering its chain goes wasted - an even more useful coin (from the POV of those who like to find Cunningham chains, especially to set records) would have a way to somehow preserve such chains rather than letting them dissappear in the ether. – Joe Pineda Feb 12 '14 at 13:09
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    @MeniRosenfeld Should Primecoin (and its clones) become much more valuable over time, I'm sure we'll see a whole new generation of chips dedicated specifically to the task of priving primality of a number and/or attempting to factorize a it - which would have deep implications for cryptography everywhere. In a way, that'd be even more useful than finding long Cunningham chains or Mersenne primes just for the sake of it. – Joe Pineda Feb 12 '14 at 13:11
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Bitcoin mining is useful work, it secures the Bitcoin block chain. If you want to pay people to do other kinds of work, you can certainly do that, but that has nothing to do with Bitcoin mining. The work Bitcoin miners do is precisely the work needed to secure the Bitcoin block chain.

There is no known way to make something be both protein folding and also secure the Bitcoin block chain, any more than you can make doing your taxes also protein folding. Hashing wasn't picked arbitrarily, it was picked because it secures the Bitcoin block chain.

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    Isn't that exactly what Primecoin does? – Steven Roose Jan 25 '14 at 15:14
  • Not really. Finding bitwin chains or Cunningham chains is not really useful. – David Schwartz Jan 26 '14 at 6:35
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    Cunningham chains are now considered useful in cryptographic systems since "they provide two concurrent suitable settings for the ElGamal cryptosystem ... [which] can be implemented in any field where the discrete logarithm problem is difficult." - Wikipedia – Steven Roose Jan 26 '14 at 20:23
  • @StevenRoose: Cunningham chains are useful in the same sense that prime numbers are useful. But finding Cunningham chain records just for the sake of it is just as useless as finding prime number records. – Meni Rosenfeld Feb 12 '14 at 8:04
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In addition to PrimeCoin, there was also PermaCoin proposed as a solution to archival of public knowledge:

Excerpt from the abstract:

We propose a modification to Bitcoin that repurposes its mining resources to achieve a more broadly useful goal: distributed storage of archival data. We call our new scheme Permacoin. Unlike Bitcoin and its proposed alternatives, Permacoin requires clients to invest not just computational resources, but also storage. Our scheme involves an alternative scratch-off puzzle for Bitcoin based on Proofs-of-Retrievability (PORs). Successfully minting money with this SOP requires local, random access to a copy of a file. Given the competition among mining clients in Bitcoin, this modified SOP gives rise to highly decentralized file storage, thus reducing the overall waste of Bitcoin.

The full paper can be found here: https://www.cs.umd.edu/~elaine/docs/permacoin.pdf

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