Math Is Fun Forum

A more generic solution:

Each time a random number is needed, everybody generates a random real between 0 and 1 and publishes a one-way hash of it.  When all hashes are received, everybody publishes the generated number and the number used is the decimal part of the sum.  (the "sum mod 1").
If you need a number from 1 to 6, compute 1+int(6*(consolidated random number)).
The number must have enough bits to prevent brute-force searching of the other's random numbers.  Or it must be padded with additional random bits.
This way, everybody can guarantee the randomness of the number.

If you need to pick a card, instead of ordering them from the start, keep track of the set of unused cards.  To pick a card, choose it by picking a random number between 1 and the number of remaining cards.

OK, the problem is, it is very intensive in mail exchanges.  So if you really want to play by mail, you better automate the part that deals with generating a distributed random number.

106227 = 99*1073.

Of course there is.  >>