Analogue Correspondence Card Games

To play a card game like poker by correspondence would require the decks to be exactly the same sequence in both locations similar to correspondence chess where the boards must be exactly the same states in both locations. (For simplicity I am speaking on the assumption of two players, but for n players the rule remains.)

However unlike chess where the players can openly see the state of the board, the players in a card game like poker must be unaware of the state of the deck. This makes things trickier, and so both players must perform a shared seeded blind shuffle of their decks, the goal being to have both shuffle their decks fairly but result in the same unknown sequences.

I suppose that one, or both players roll two dice repeatedly and confer on the results. For example the pairs (6,2) (5,6) (2,4) (6,6) (…etc) might be rolled and shared.

With the above rolls agreed, the players would then perform the following example on same ordered decks of cards (here we will use the first rolled pair above); split the deck into 6, then rotate the 2nd card up rightwards a place. If a card overflows the end of the split segment then it rotates to the start of the split segment. Then rebuild the deck in the reverse order it was split. If one is rolled for the first of the dice pair, then the deck is not split but the cards are still rotated as described.

If the above example is followed then both decks in both locations should be shuffled exactly the same, and very hard or impossible to accurately deduce casually (unless someone is adamant on cheating). Now because both states of the deck are the same in both locations, a game like poker can proceed by correspondence. Both players should agree prior to playing how many rolls they are both satisfied with,

The flaw of this is that people are prone to mistakes, so a handshake to confirm matching shuffles could be performed before any play is commenced by sacrificing n top cards of the deck, if both players confirm that the first n cards match, then they can assume with some allowance for a degree of error that the decks are shuffled in the same order in two separate places.

The alternative is of course ignoring this method and both shuffling decks independently with the knowledge that quirks like duplicate cards may occur. I have done this many times in correspondence card games and it’s been absolutely fine.