"Why would characters spend time answering imaginary questions to fictional hypotheticals?" ... There is a certain genre of "Hot Network Questions" titles which make me cringe

Then there's this (which isn't in that category)

Basically, how do I make a coin operated turnstile that can't be cheated with no human guards and using only medieval technology...

That question raises so many other questions. How high-tech is too high-tech? Why do you care if occasionally two super skinny people cheat the system? How do you make a coin operated device with that level of technology? If you give people access to stone or wood cutting tools and have no human involvement what's stopping counterfeit coin making?

That's kind of sort of loosely crypto related. I mean that people propose that kind of stuff all the time. People seem to think biometric stuff is secure to use everywhere for some reason. (Even without guards to look for tampering or unusual behavior.)

@J.J It's probably using CBC mode, so investigate attacks on CBC mode with a fixed IV

There are definitely questions about the padding oracle attack on the main site here, have you investigated any of them?

(And if there weren't any, you'd be free to ask about it!)