[avidiax]

Yeah, it's a bit surprising that these bill validators are so robust, given that most security systems are a game of raising the difficulty just high enough to be less attractive than other criminal opportunities. It might be that two detection methods was too easy to subvert, so a third is added, and this makes it excessively secure.

Certainly, the tubular lock on most vending machines is vulnerable to a variety of attacks, so, if a criminal wants a snickers bar and maybe a lockbox of cash, buying a tubular lock pick is far more expedient than trying to counterfeit bills.

I am wondering if the author maybe didn't check whether 2 of 3 factors would be sufficient. It could be that the bill validators allow 1 of 3 factors to be out of spec to increase acceptance rate.

[dpoloncsak]

FWIW, lock picking is shockingly simple to get the hang of.

It's almost always far more expedient than doing whatever else...especially if you learn zipping or how to use a city rake effectively