<p>PoW needs to be hard to do but easy to verify (by a computer). There is very little left that humans are better at than computers (OCR, face and image recognition, IBM Watson [1] etc.). And probably nothing is easily computer verifiable.</p>
<p>One example are captchas. The ones that don't get read by OCR, simply get outsourced to children in poor countries. You might say: still proof of human work, but there is no way for a computer to verify the result. On top of that captchas don't satisfy some other requirements for PoW.</p>
<p>One such requirement is that the work is progress-free. Another: whatever the &quot;puzzle&quot; is, it must not be known beforehand as that would allow people to start the race early. This also implies there may not be one person or group of people that have access to the puzzles in advance as they would have to be trusted to not cheat (i.e. the system would not be trustless).</p>
<p>[1] <a href="https://en.m.wikipedia.org/wiki/Watson_(computer)" rel="nofollow noreferrer">https://en.m.wikipedia.org/wiki/Watson_(computer)</a></p>

CC BY-SA 4.0
2015-10-29T01:54:57.107Z
2023-01-21T20:20:38.450Z
2023-01-21T20:20:38.450Z
Jannes
<p>Something like this has been created and it is called Idena.</p>
<blockquote>
<p>Idena is a novel way to formalize people on the blockchain. It does
not collect or store personally identifiable information. Idena proves
the humanness and uniqueness of its participants by running an AI-hard
Turing test at the same time for everyone around the globe.</p>
<p>The Idena blockchain is driven by proof-of-person consensus: Every
node is linked to a cryptoidentity, one single person with equal
voting power.</p>
</blockquote>
<p>Website:
<a href="https://idena.io/" rel="nofollow noreferrer">https://idena.io/</a></p>
<p><a href="https://i.sstatic.net/WLQTH.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/WLQTH.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2020-08-02T19:22:50.957Z
2020-08-02T19:22:50.957Z
More
<p>Yes, there is a paper about: "Designing Proof of Human-work Puzzles for Cryptocurrency
and Beyond"
<a href="https://eprint.iacr.org/2016/145.pdf" rel="nofollow">https://eprint.iacr.org/2016/145.pdf</a></p>

CC BY-SA 3.0
2016-03-23T14:05:37.180Z
The linked paper addresses this exact question and is very interesting. However, it would be helpful to also have a description of the concepts here in the answer. Otherwise this seems more like a comment.
trichoplax is on Codidact now
CC BY-SA 3.0
2017-05-26T20:15:21.253Z
The solution in the paper depends on cryptographic computer program obfuscation. Unfortunately, cryptographic code obfuscation is known to be impossible since around 2000 (there is a mathematical proof that these programs cannot be obfuscated). To make matters worse, cryptographic obfuscation goes far beyond any of the cryptography that we have today since a good enough cryptographic code obfuscator will be able to solve all of the problems in cryptography. The technology required to make this proof-of-work puzzle work simply does not exist.
Joseph Van Name
CC BY-SA 3.0
2016-03-23T12:29:02.867Z
2016-03-23T12:29:02.867Z
jaceved2
<p>I designed one between 2015 and 2018, and had implemented it in full by 2021. It achieves the same goals as &quot;proof of human work&quot; concept. It gained some popularity in 2015 and likely led to some of the other similar projects that you've seen, that started later. I eventually named it after Bitcoin: <a href="https://bitpeople.org" rel="nofollow noreferrer">https://bitpeople.org</a></p>
<p>The &quot;work&quot; done by &quot;miners&quot; (that grants them right to sign and publish a block), is: video chat Turing test, more or less. The imitation game, as Alan Turing called it. This is the hardest &quot;digital&quot; problem for a computer to solve, and therefore the most secure digital &quot;proof of human work&quot; (proof of unique human, granted that the idea to use &quot;human work&quot; for mining relates, somehow, to one-person-one-vote analogous with one-cpu-one-vote in proof-of-work) that can be generated.</p>

CC BY-SA 4.0
2023-08-19T21:17:31.823Z
2023-08-19T21:17:31.823Z
BipedalJoe
<p>There are many different schemes of Proof of Human Work (PoH or PoHw), though <a href="https://www.miftycoin.com" rel="nofollow noreferrer">https://www.miftycoin.com</a> is the only one known to be a real implementation publicly available. In the case of MiftyCoin, block validation is performed by humans solving puzzles. Each puzzle is unique to each solver, as it is a function of the block identifier, the solver’s address hash and the transaction hashes.</p>
<p>A whitepaper on MiftyCoin can be found here:
<a href="https://arxiv.org/pdf/2211.14444" rel="nofollow noreferrer">https://arxiv.org/pdf/2211.14444</a></p>
<p>Disclaimer: I am the creator of MiftyCoin.</p>

CC BY-SA 4.0
2023-01-23T01:45:50.810Z
Agreed. Done. Thanks for the suggestion!
Javier A. Arroyo-Figueroa
CC BY-SA 4.0
2023-01-23T21:32:36.430Z
Your paper makes no sense. You assert that human capacity exceeds machine capacity to solve your problem, but it doesn't. Both humans and computers would use trial and error to solve it, and computers can try thousands of times more frequently than a human could. How many attempts per second do you think a human could make? Fewer than one, no? And a computer could easily do many attempts per second.
David Schwartz
CC BY-SA 4.0
2023-02-02T15:01:30.040Z
You are correct if the assumption is that attempt is only by trial and error; in which the machine will always win, but only if given enough time. For a 24-tile puzzle, each tile has 4 possible moves, then the total number of trials is 4^24 = 281,474,976,710,656 moves. Even with a very fast single-processor unit that can process 1x10^9 trials per second, this amounts to more than 281,000 seconds = 3 days which is far from the 10-minute limit.
Javier A. Arroyo-Figueroa
CC BY-SA 4.0
2023-02-02T18:55:42.410Z
So then is the paper complete nonsense? Or do you think there's some method humans could use to solve these problems that computers could not use? Your paper doesn't explain its sole claim -- that humans will be better at solving these problems than computers are. How do you expect humans to solve them?
David Schwartz
CC BY-SA 4.0
2023-02-05T04:56:35.547Z
Finding an optimal solution to a problem with a large search space like the 24-tile puzzle is an NP-hard problem; in our case there can be more than one solution, as the goal is not to find a specific arrangement but an arrangement that brings the highest score. This paper is a good start to learn more about the type of problem we are solving: https://courses.cs.washington.edu/courses/csep573/10wi/korf96.pdf
Javier A. Arroyo-Figueroa
CC BY-SA 4.0
2023-02-05T22:05:00.777Z
The paper is complete nonsense. Computers are better at solving this class of problems than humans are -- orders of magnitude better. So this class of problem is useless as proof of human work. A single computer would easily do more of this type of work than a hundred humans could. It is not sufficient that you find a problem that is hard for computers to do -- PoW systems use those -- it must be easier for humans to do than it is for computers to do! The MiftyCoin paper is complete nonsense.
David Schwartz
CC BY-SA 4.0
2023-02-10T12:31:25.013Z
I think you need a better understanding of problem classes like P, EXP, NP, NP-Complete and NP-hard; otherwise this will lead to an endless debate. Saying " computers are better at solving this class of problems" is an over-simplication. There are problems that computers cannot solve due to either time or space complexity. may games fall into that category.
Javier A. Arroyo-Figueroa
CC BY-SA 4.0
2023-02-10T20:33:43.827Z
Sorry, you're talking nonsense. Humans can't *solve* this problem either. But computers can attempt to solve this problem by trial and error. Humans have no method that is anywhere close to as effective as a computer using mostly its superior brute force. You have no rational basis to believe that the results you choose where made by humans rather than computers and it is clearly *much* more likely that computers made them.
David Schwartz
CC BY-SA 4.0
2023-01-21T14:29:14.973Z
2023-01-23T01:46:39.803Z
2023-01-23T01:46:39.803Z
Javier A. Arroyo-Figueroa
<p>There have been suggestions of proof of work requirements that exclude GPUs or ASICS (or try to) but I was wondering if anyone had suggested a proof of work that is not suited to being solved by computer at all, so that the miners would be humans working on proving their own work done - work that cannot (currently) be performed by a computer in a competitive amount of time.</p>

<p>This would presumably need to be quickly verifiable by computer, but not independently solvable by computer.</p>

<p>If this hasn't yet been proposed, is there any apparent reason this would not work?</p>

CC BY-SA 3.0
2015-10-28T21:42:00.767Z
It won't work because we haven't found anything simple enough for the majority of humans to do, while being both computer-verifiable and too difficult for a computer to do (see: all the failed variations on CAPTCHA).
Mark
CC BY-SA 4.0
2023-08-20T22:45:11.260Z
@Mark there is a very easy solution, but it is hard to realize it. Let humans do the verification, not computers. Pair every person in the world 1-on-1, to do a simultaneous verification event. Do the event monthly, mix all proofs from month to month, making it fully anonymous. Simple enough for the majority of humans to do, difficult (impossible really, but, at least difficult) for a computer to do.
BipedalJoe
<proof-of-work>
Has anyone proposed a human only proof of work system?
trichoplax is on Codidact now
# Has anyone proposed a human only proof of work system?

(Asked by: username_0 on 2015-10-28)

There have been suggestions of proof of work requirements that exclude GPUs or ASICS (or try to) but I was wondering if anyone had suggested a proof of work that is not suited to being solved by computer at all, so that the miners would be humans working on proving their own work done - work that cannot (currently) be performed by a computer in a competitive amount of time.

This would presumably need to be quickly verifiable by computer, but not independently solvable by computer.

If this hasn't yet been proposed, is there any apparent reason this would not work?

**Tags:** proof-of-work

> **Comments:**
> **username_1**: It won't work because we haven't found anything simple enough for the majority of humans to do, while being both computer-verifiable and too difficult for a computer to do (see: all the failed variations on CAPTCHA).  
> **username_2**: @username_1 there is a very easy solution, but it is hard to realize it. Let humans do the verification, not computers. Pair every person in the world 1-on-1, to do a simultaneous verification event. Do the event monthly, mix all proofs from month to month, making it fully anonymous. Simple enough for the majority of humans to do, difficult (impossible really, but, at least difficult) for a computer to do.  

---

## 5 answers

### Answer by username_3 on 2015-10-29. Score: 3

PoW needs to be hard to do but easy to verify (by a computer). There is very little left that humans are better at than computers (OCR, face and image recognition, IBM Watson [1] etc.). And probably nothing is easily computer verifiable.

One example are captchas. The ones that don't get read by OCR, simply get outsourced to children in poor countries. You might say: still proof of human work, but there is no way for a computer to verify the result. On top of that captchas don't satisfy some other requirements for PoW.

One such requirement is that the work is progress-free. Another: whatever the "puzzle" is, it must not be known beforehand as that would allow people to start the race early. This also implies there may not be one person or group of people that have access to the puzzles in advance as they would have to be trusted to not cheat (i.e. the system would not be trustless).

[1] <https://en.m.wikipedia.org/wiki/Watson_(computer)>


---

### Answer by username_4 on 2020-08-02. Score: 2

Something like this has been created and it is called Idena.

> Idena is a novel way to formalize people on the blockchain. It does
> not collect or store personally identifiable information. Idena proves
> the humanness and uniqueness of its participants by running an AI-hard
> Turing test at the same time for everyone around the globe.
>
> The Idena blockchain is driven by proof-of-person consensus: Every
> node is linked to a cryptoidentity, one single person with equal
> voting power.

Website:
<https://idena.io/>

[![enter image description here](https://i.sstatic.net/WLQTH.png)](https://i.sstatic.net/WLQTH.png)


---

### Answer by username_5 on 2016-03-23. Score: 2

Yes, there is a paper about: "Designing Proof of Human-work Puzzles for Cryptocurrency
and Beyond"
<https://eprint.iacr.org/2016/145.pdf>

> **Comments:**
> **username_0**: The linked paper addresses this exact question and is very interesting. However, it would be helpful to also have a description of the concepts here in the answer. Otherwise this seems username_4 like a comment.  
> **username_6**: The solution in the paper depends on cryptographic computer program obfuscation. Unfortunately, cryptographic code obfuscation is known to be impossible since around 2000 (there is a mathematical proof that these programs cannot be obfuscated). To make matters worse, cryptographic obfuscation goes far beyond any of the cryptography that we have today since a good enough cryptographic code obfuscator will be able to solve all of the problems in cryptography. The technology required to make this proof-of-work puzzle work simply does not exist.  

---

### Answer by username_2 on 2023-08-19. Score: 0

I designed one between 2015 and 2018, and had implemented it in full by 2021. It achieves the same goals as "proof of human work" concept. It gained some popularity in 2015 and likely led to some of the other similar projects that you've seen, that started later. I eventually named it after Bitcoin: <https://bitpeople.org>

The "work" done by "miners" (that grants them right to sign and publish a block), is: video chat Turing test, username_4 or less. The imitation game, as Alan Turing called it. This is the hardest "digital" problem for a computer to solve, and therefore the most secure digital "proof of human work" (proof of unique human, granted that the idea to use "human work" for mining relates, somehow, to one-person-one-vote analogous with one-cpu-one-vote in proof-of-work) that can be generated.


---

### Answer by username_7 on 2023-01-21. Score: -1

There are many different schemes of Proof of Human Work (PoH or PoHw), though <https://www.miftycoin.com> is the only one known to be a real implementation publicly available. In the case of MiftyCoin, block validation is performed by humans solving puzzles. Each puzzle is unique to each solver, as it is a function of the block identifier, the solver’s address hash and the transaction hashes.

A whitepaper on MiftyCoin can be found here:
<https://arxiv.org/pdf/2211.14444>

Disclaimer: I am the creator of MiftyCoin.

> **Comments:**
> **username_7**: Agreed. Done. Thanks for the suggestion!  
> **username_8**: Your paper makes no sense. You assert that human capacity exceeds machine capacity to solve your problem, but it doesn't. Both humans and computers would use trial and error to solve it, and computers can try thousands of times username_4 frequently than a human could. How many attempts per second do you think a human could make? Fewer than one, no? And a computer could easily do many attempts per second.  
> **username_7**: You are correct if the assumption is that attempt is only by trial and error; in which the machine will always win, but only if given enough time. For a 24-tile puzzle, each tile has 4 possible moves, then the total number of trials is 4^24 = 281,474,976,710,656 moves. Even with a very fast single-processor unit that can process 1x10^9 trials per second, this amounts to username_4 than 281,000 seconds = 3 days which is far from the 10-minute limit.  
> **username_8**: So then is the paper complete nonsense? Or do you think there's some method humans could use to solve these problems that computers could not use? Your paper doesn't explain its sole claim -- that humans will be better at solving these problems than computers are. How do you expect humans to solve them?  
> **username_7**: Finding an optimal solution to a problem with a large search space like the 24-tile puzzle is an NP-hard problem; in our case there can be username_4 than one solution, as the goal is not to find a specific arrangement but an arrangement that brings the highest score. This paper is a good start to learn username_4 about the type of problem we are solving: https://courses.cs.washington.edu/courses/csep573/10wi/korf96.pdf  
> **username_8**: The paper is complete nonsense. Computers are better at solving this class of problems than humans are -- orders of magnitude better. So this class of problem is useless as proof of human work. A single computer would easily do username_4 of this type of work than a hundred humans could. It is not sufficient that you find a problem that is hard for computers to do -- PoW systems use those -- it must be easier for humans to do than it is for computers to do! The MiftyCoin paper is complete nonsense.  
> **username_7**: I think you need a better understanding of problem classes like P, EXP, NP, NP-Complete and NP-hard; otherwise this will lead to an endless debate. Saying " computers are better at solving this class of problems" is an over-simplication. There are problems that computers cannot solve due to either time or space complexity. may games fall into that category.  
> **username_8**: Sorry, you're talking nonsense. Humans can't *solve* this problem either. But computers can attempt to solve this problem by trial and error. Humans have no method that is anywhere close to as effective as a computer using mostly its superior brute force. You have no rational basis to believe that the results you choose where made by humans rather than computers and it is clearly *much* username_4 likely that computers made them.  

---

