3 ms·

Have the CAPCHA require properly constructing a nonlinear programming problem to solve an optimization problem, where the requirements are not expressed in term

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.

robertlagrant 5y ago
Good idea! To prove you are a human, mine three Bitcoin.
- meowface 5y ago
  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.
- hsbauauvhabzb 5y ago
  Why not something computationally expensive? Bcrypt this value 10000 times to continue
  - sodality2 5y ago
    Ideally you'd have something that's hard for the client but easy for the server to verify, though. so maybe prime factoring?
    - tshaddox 5y ago
      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.
      - wruza 5y ago
        What nonceness!
  - kalleboo 5y ago
    Spammers use botnets, so they have plenty of computation available
    - immibis 5y ago
      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
  - iszomer 5y ago
    Imagine when a miner is used as Captcha and would only pass when a certain amount has been mined..