[ecolonsmak]

"...unique tracking label for every card in the deck"

I'd like more details on how this was accomplished on a practical level. Got me thinking about how to embed trackers thin enough to go into a playing card that would operate like a mesh network then the deck could self report once it's properly randomized making a green light go off indicating play may begin.

[layer8]

They didn’t do this practically, the “tracking label” is just an analogy to convey what they did mathematically. The word “barcode” is also only used because it might be more accessible to the layperson than “bit sequence”.

[hdndjsbbs]

This is just the authors explanation to explain how to encode where a card ends up. The cards don't actually have barcodes, they have a binary-encoded number where a 0 indicates the left pile and 1 indicates the right pile during a specific round of the shuffle. The number encodes the journey that card makes during the shuffle. It's not an actual barcode.

[empath75]

There are actually "marked" decks you can buy that come with an iphone app that tell you exactly where every card on the deck is by looking at the side.

[WorldMaker]

Marked decks are an ancient tradition for both cheaters and magicians. There are also ways to mark a deck that aren't obvious to most people with a casual inspection and that don't need an app to read from the edge.

[empath75]

Yeah, but there aren't ones that will give you the _entire stack_ in less than a second from a glance at the side of the deck.

[WorldMaker]

You might be surprised at how close they sometimes get, at a glance. For close up magic it has to be readable at a quick glance (without an app). For some of the cheating it has to "not even be a glance" because you can't get caught looking at the side of a deck.

To be fair, sure most of those marking strategies are approximations designed for a specific trick or a specific gambling game and so don't always need to be 100% of the state information (suit and rank of every individual card). But there are certainly close up magic reasons to have a deck you can find exact cards by marks. Though also to be fair, many (but not all) of those do move the marks to the back of the card with the assumption that you can at least spread the backs of the cards.