Re: Cryptographic protocols, again

2 years ago I've been thinking about this on my side, just for fun
(I'm no expert at all in cryptograph).
To me, playing for money online requires something that guarantees the
randmoness/non-manipulation of
the dice/cards. Also, I would feel more comfortable if the method
would not involve a third party (you will
never be sure the third party is not corrupted/biased).

I came up with something like this (imagine for a second bg is played
with a single dice, extension is trivial):

1- Before the game:
1.1- Each player generates (whichever manner) on his side a long
(10000) sequence of numbers in the range 1-6
1.2- Each player encrypts its entire sequence with a key and sends
it to the opponent.

2- During the game:
2.1- At each turn, each player pops a number from its sequence and
sends it to the other player.
2.2- The player on roll sums (modulo 6, +1) the 2 numbers to obtain
the value of the dice (player not on roll does the same, to verify).

3- At the end of the game/match:
3.1- Each player communicates its own key, so that each player can
decrypt the entire other player's sequence and check that it matches
the communicated numbers.

I'm not sure if, once we have used most of the numbers in the
sequence, the key could become easy to crack (disclosing the rest of
the sequence), that may depend on the chosen algortihm. Possible
solution: if the sequence is 10000 numbers, generate a new one as soon
as you've eaten up 50% of it (or whichever percentage is considered as
safe from a cryptographic point of view), eventually encrypt it with a
different key.

The thing I like most of this is that the sequences are "available"
before the match: it's like having the list of rolls locked in a chest
before the match, but being allowed to open it only at the end of the
match. This should avoid ad-hoc dice manipulations, i.e. giving a
large double in a race to the player that is below in the score, to
make the match more excting or to favor the underdog.

MaX.


.

Relevant Pages

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