[Cryptography] Real-world crypto/PRNG problem: Bridge

[Jon Callas]

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> On Aug 23, 2016, at 12:38 PM, Bill Frantz <frantz at pwpconsult.com> wrote:
> 
> Typically in rubber bridge, the cards get shuffled 3 or 4 times before being dealt again. This turned out to be far too few mixings. I think I remember recommendations for 7 or so mixings, but I'm not sure even this level is enough.

There has been a lot of research on this over the years. Myself, I did a model of shuffling for a statistics class many years ago. So many that it was written in Fortran. I modeled in it things like how many cards you'd drop in each flick of the shuffle statistically.

My numbers, which jibe with what I've read from other people doing the same is a minimum of five, and preferably eight. By the time you get to eight shuffles, it's hard to see badness any more. Since each hand is the set of cards that are all N mod 4, a card moving from the top (position 0) to position 3 is equivalent to it moving all the way to the bottom (position 51).

	Jon


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