Matthew Johnson wrote:
> (sorry for the long post!)
>
> Being a poor student club we can't afford a duplimate machine but is
> nice to have some of the benefits, like handouts and double dummy
> analysis etc. It can also be nice to generate specific hands for
> certain events.
>
> To solve this, I invented a scheme for producing duplicated boards
> without a duplimate machine. It also doesn't allow the people
> involved in the process to know what the hands are so it can be done
> by the players themselves.
>
> A more complete description was presented at the 2008 International
> Workshop on Security Protocols and the paper is available for
> download[0]. The software used to run it is also available[1] along
> with a how-to do***ent for people doing the duplication[2].
>
> I'm posting to rec.games.bridge to see what the wider bridge
> community thinks about the system and what types of game it might be
> suitable for use in.
>
> A quick description of the system is as follows. The computer
> generates random hands, or loads them from sims files, or whatever,
> and does DD analysis. There are many programs which will do this some
> of which are free. It's obviously easy to then print hand records.
> The duplicating program then generates two pseudo-random permutations
> which individually reveal nothing about the desired hand, but when
> applied in order, starting from a sorted deck of cards, but when
> applied in order produce the desired hand.
>
> These permutations are given to two separate players (possibly on
> different teams) who each do half of the process. The first player
> stacks up the piles after their deal and pass them to the other
> player. The second player puts the resulting hands in the boards.
>
> Permutations look like:
>
> 3121 2131 4431 4431 4242 ...
>
> and give the order to deal the cards into four piles.
The paper makes for quite interesting reading.
With regard to section 4, which discusses some possible problems with
card identification and probabilities, and suggests varying the pile
sizes during the first "deal", other possible solutions would be to
change (or randomly vary) the number of piles, or randomly vary the
order of "pile assembly" when putting the deck back together in
preparation for the second "deal".
--
Steve Foster
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