<p>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:</p>

<ul>
<li><p>Easy to verify solutions</p></li>
<li><p>Hard to find solutions</p></li>
<li><p>Difficulty of finding solutions can be precisely quantified</p></li>
<li><p>Provably inseparable from the block it secures</p></li>
</ul>

<p>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".)</p>

<p>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.</p>

CC BY-SA 3.0
2014-01-21T09:47:02.387Z
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
CC BY-SA 3.0
2014-01-25T15:03:55.737Z
Quite right @DavidSchwartz, amended my answer.
paralogical
CC BY-SA 3.0
2014-02-12T13:23:56.317Z
@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
CC BY-SA 3.0
2014-02-12T13:30:27.047Z
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
CC BY-SA 3.0
2014-01-21T07:37:17.900Z
2018-04-09T10:28:32.157Z
2018-04-09T10:28:32.157Z
paralogical
<p>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.</p>

<p>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.</p>

CC BY-SA 3.0
2014-01-25T15:14:57.153Z
Isn't that exactly what Primecoin does?
Steven Roose
CC BY-SA 3.0
2014-01-26T06:35:12.007Z
Not really. Finding bitwin chains or Cunningham chains is not really useful.
David Schwartz
CC BY-SA 3.0
2014-01-26T20:23:34.850Z
`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](https://en.wikipedia.org/wiki/Cunningham_chain)
Steven Roose
CC BY-SA 3.0
2014-02-12T08:04:50.557Z
@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
CC BY-SA 4.0
2024-03-01T20:10:37.383Z
@DavidSchwartz have you heard of "killing two birds with one stone"?
Benjamin Grange
CC BY-SA 3.0
2014-01-21T04:33:12.467Z
2014-01-21T04:33:12.467Z
David Schwartz
<p>In addition to PrimeCoin, there was also PermaCoin proposed as a solution to archival of public knowledge: </p>

<p>Excerpt from the abstract:</p>

<blockquote>
  <p>We propose a modification to Bitcoin that repurposes its mining resources to achieve a more broadly useful goal: <strong>distributed storage of archival data</strong>. 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 <strong>based on Proofs-of-Retrievability (PORs)</strong>. 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.</p>
</blockquote>

<p>The full paper can be found here:
<a href="https://www.cs.umd.edu/~elaine/docs/permacoin.pdf" rel="noreferrer">https://www.cs.umd.edu/~elaine/docs/permacoin.pdf</a></p>

CC BY-SA 3.0
2014-09-24T11:27:06.563Z
2014-09-24T15:05:52.907Z
2014-09-24T15:05:52.907Z
user19438
<p>Well, I know of one altcoin that does useful work: <a href="http://primecoin.org">Primecoin</a>.</p>

<p>As <a href="https://en.wikipedia.org/wiki/Primecoin">Wikipedia</a> describes it:</p>

<blockquote>
  <p>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.</p>
</blockquote>

<p>Primecoin already has quite some world-record prime chains on it's name: some <a href="https://en.wikipedia.org/wiki/Cunningham_chain#Largest_known_Cunningham_chains">Cunningham chains</a> and some <a href="https://en.wikipedia.org/wiki/Bi-twin_chain#Largest_known_bi-twin_chains">Bi-twin chains</a>.</p>

CC BY-SA 3.0
2014-02-12T08:07:52.210Z
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
CC BY-SA 3.0
2014-02-12T13:09:45.137Z
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
CC BY-SA 3.0
2014-02-12T13:11:50.583Z
@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
CC BY-SA 3.0
2014-01-25T15:18:17.323Z
2014-01-25T15:18:17.323Z
Steven Roose
<p>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?</p>

CC BY-SA 3.0
2014-01-21T04:16:01.697Z
Your question is based on the assumption that securing the Bitcoin block chain is useless.
David Schwartz
CC BY-SA 3.0
2014-01-21T04:26:23.850Z
@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
CC BY-SA 3.0
2014-01-21T04:31:51.053Z
See my answer. Protein folding has nothing to do with Bitcoin mining.
David Schwartz
CC BY-SA 3.0
2015-04-22T08:27:11.850Z
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
CC BY-SA 4.0
2021-10-18T22:50:50.943Z
Require the Miners to walk on treadmills to generate the Electricity for their Computers while they solve their Hash problems. This can be verified and quantified.
Pseudoego
<proof-of-work><algorithms><mining-theory>
Why can't we design a bitcoin that does useful work?
Dokkat
# Why can't we design a bitcoin that does useful work?

(Asked by: username_0 on 2014-01-21)

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?

**Tags:** proof-of-work, algorithms, mining-theory

> **Comments:**
> **username_1**: Your question is based on the assumption that securing the Bitcoin block chain is useless.  
> **username_0**: @username_1 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.  
> **username_1**: See my answer. Protein folding has nothing to do with Bitcoin mining.  
> **username_2**: 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.  
> **username_3**: Require the Miners to walk on treadmills to generate the Electricity for their Computers while they solve their Hash problems. This can be verified and quantified.  

---

## 4 answers

### Answer by username_4 on 2014-01-21. Score: 18

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.

> **Comments:**
> **username_1**: You missed the most important requirement -- the work must be provably inseparable from the block it secures. Otherwise, it fails to secure the block.  
> **username_4**: Quite right @username_1, amended my answer.  
> **username_5**: @username_0 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...  
> **username_5**: 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 :)  

---

### Answer by username_6 on 2014-01-25. Score: 9

Well, I know of one altcoin that does useful work: [Primecoin](http://primecoin.org).

As [Wikipedia](https://en.wikipedia.org/wiki/Primecoin) 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](https://en.wikipedia.org/wiki/Cunningham_chain#Largest_known_Cunningham_chains) and some [Bi-twin chains](https://en.wikipedia.org/wiki/Bi-twin_chain#Largest_known_bi-twin_chains).

> **Comments:**
> **username_7**: 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.  
> **username_5**: 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.  
> **username_5**: @username_7 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.  

---

### Answer by username_1 on 2014-01-21. Score: 7

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.

> **Comments:**
> **username_6**: Isn't that exactly what Primecoin does?  
> **username_1**: Not really. Finding bitwin chains or Cunningham chains is not really useful.  
> **username_6**: `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](https://en.wikipedia.org/wiki/Cunningham_chain)  
> **username_7**: @username_6: 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.  
> **username_8**: @username_1 have you heard of "killing two birds with one stone"?  

---

### Answer by username_9 on 2014-09-24. Score: 7

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>


---

