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A comment on DOOM Captcha. Parent comment

Re:DOOM Captcha by lamontcg on Monday May 24, 2021 @05:07PM (#27269713)
Have the CAPCHA require properly constructing a nonlinear programming problem to solve an optimization problem, where the requirements are not expressed in terms of the NLP and the human has to design it.

Which would have the side effect of putting the bot makers to work on useful and hard problems to solve.

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Re:DOOM Captcha by robertlagrant on Monday May 24, 2021 @05:08PM (#27269726)
Good idea! To prove you are a human, mine three Bitcoin.
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Re:DOOM Captcha by meowface on Monday May 24, 2021 @07:33PM (#27270965)
Spam and DoS prevention were actually the original purpose of Proof of Work. Hashcash, the first (I think) anti-spam PoW algorithm, was what Bitcoin's PoW algorithm was inspired by.
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Re:DOOM Captcha by hsbauauvhabzb on Monday May 24, 2021 @08:41PM (#27271440)
Why not something computationally expensive? Bcrypt this value 10000 times to continue
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Re:DOOM Captcha by sodality2 on Monday May 24, 2021 @10:45PM (#27272109)
Ideally you'd have something that's hard for the client but easy for the server to verify, though. so maybe prime factoring?
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Re:DOOM Captcha by tshaddox on Tuesday May 25, 2021 @12:38AM (#27272643)
Or, the server provides a random string of bits with length n and requires a string of bits with length n+m that starts with the provided n bits and whose SHA-1 hash begins with 20 zero bits.
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Re:DOOM Captcha by wruza on Tuesday May 25, 2021 @03:55AM (#27274104)
What nonceness!
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Re:DOOM Captcha by iszomer on Tuesday May 25, 2021 @01:43PM (#27279881)
Imagine when a miner is used as Captcha and would only pass when a certain amount has been mined..
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Re:DOOM Captcha by kalleboo on Tuesday May 25, 2021 @09:15AM (#27276402)
Spammers use botnets, so they have plenty of computation available
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Re:DOOM Captcha by immibis on Sunday May 30, 2021 @08:25AM (#27332743)
And if every site does this, they have plenty less. Imagine if you can only attempt your spam 20 times per second instead of 20000
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