Timothy May writes:-

An obvious problem with crypto card games is this: what does it provide that is worth the extra effort of doing encryption?

Quite so. What other sorts of games are there that could benefit from crypto? There are a large number of multiplayer board games which combine high levels of complexity in move options with the necessity for inter-player diplomacy. Such board games are suitable for play-by-email (PBEM), as players need time to negotiate and work out moves. They generally work by requiring all players to submit orders for their move by a deadline. Problems with PBEM of such games revolve around having to persuade one person to sit out and adjudicate player moves (the luckless 'games master' or GM). There is a die roll server (send 'help' to dice@danpost4.uni-c.dk for details) which can provide die rolls for game functions but a person is still needed to request the appropriate die rolls to resolve player orders. The solution here is crypto. You can do away with the need for an extra person as GM by having one of the players act as GM (the 'player-GM') and resolve moves for each turn. Since all moves are due by one deadline there is the risk that the player-GM can move in response to other player's moves which have been sent to the player-GM for resolution. To prevent this the player-GM must make their move before all the other players. If done using plain text this puts the player-GM at a disadvantage so their orders are encrypted before emailing to all other players. These encrypted orders cannot then be changed in response to other player orders. During move resolution all player orders are published. This benefits all players in that they can check that the player-GM has resolved their orders correctly (when using a non-player GM order resolution is typically hidden). These published orders would include the decrypt pass phrase for the player-GM's orders, and the plain text of those orders. It would be incumbent on one or more of the players to be able to decrypt the player-GM's orders using the decrypt pass phrase, just to check that when decrypted they match the plain text version. Player-GM offers other advantages as well. For example, players can swap the onerous role of player-GM to allow for holidays etc. Using a non-player GM, if that person drops out then the game dies. Player-GM also allows short deadlines, each successive deadline being handled by a different player-GM, which speeds up the game and spreads the GMing load. Another use of a non-player GM is to hold secret agreements between players. Using player-GM this is no longer possible, but public/private key-based encryption can be used to allow players to sign secret treaties with each other. There is a specific forfeit in many game rules for breaching a signed treaty, so the need exists to make secret deals that can later be verified by players not in on the secret deal. Once public keys have been exchanged by players then secret treaties are no problem. Persuading gamers to use crypto to play multiplayer board games PBEM does not take much doing. If no one wants to be a non-player GM (and few do) then without crypto there is no game. I am currently playing in a 7-player PBEM board game called 'Empires of the Middle Ages' using the player-GM method. We use PGP as it supports the encryption facilities needed, runs on the various platforms different players use and is free. However, player-GM and crypto have yet to make an impact in the PBEM gamer community. This community is small and the ownership of particular games is limited. The game I am playing player-GM, 'Empires of the Middle Ages', although an excellent game, has been out of print nearly 15 years. I will be trying to start other board games using crypto and player-GM in the near future. Watch rec.games.board and rec.games.pbm for announcements. I should mention that player-GM is not the only solution to the GM problem. Another answer is to code a email-driven program which will adjudicate orders. Here the problem is the inherent complexity of many board games. The most successful adjudicator program to my knowledge is the Diplomacy judge (send 'help' to judge@morrolan.eff.org for details). Diplomacy is a relatively simple board game set loosely in Europe prior to the Great War. As the game name suggests, players can only win the game by good diplomacy, as military skills are not enough on their own. Many thousands of people play PBEM Diplomacy and its variants (games which change certain rules and/or map features from the standard game). Although the Diplomacy judge allows anonymous opponents and faked email in certain Diplomacy variants, it has no built-in facilities for use of public keys, which seems to me a strange omission. More information on the Diplomacy Judge can be found in the FAQ for rec.games.diplomacy. Alan Poulter (apoulter@nyx.cs.du.edu/a.poulter@lut.ac.uk)