Dolla dolla bill, y'all: Reverse engineering a banknote validator

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48 points·voxadam··4 comments

I thought this was a fascinating read. To cut a long story short, he thought these cheap bank note detectors would be easy to fool.

But they measure several things at once, which are extremely hard to mimic in aggregate.

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.

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

The spray on sunscreen hack was wild, props!

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