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From: "Chris Adams" <adamsc@io-online.com> To: "ogren@concentric.net" <ogren@concentric.net> Date: Thu, 30 May 96 02:30:30 Reply-To: "Chris Adams" <adamsc@io-online.com> Priority: Normal X-Mailer: PMMail 1.5 UNREGISTERED SHAREWARE MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Subject: Re: [crypto] crypto-protocols for trading card gam

Disadvantages:

The entire integrity of the system relies on the security of the game company's key pair. If the secret key is comprimised, either by Cards are not transferrable. In order to make cards transferrable the game company must be able to invalidate cards which have been traded to others. In other words if Alice wants to give a cards to Bob she must: I would just have multiple validators w/separate keys. sign w/each. This would not eliminate the problem but could reduce it...

1. Contact the game company and tell them she wants to give the card to Bob. 2. The game company must issue a new card to Bob with a new serial number and with Bob's public key rather than Alice's. 3. The game company must invalidate Alice's old card. Since there is no way that the game company can make sure all copies of the card have been destroyed it must create a "invalid serial number list" and have the players dial into that list everytime the game is played.

Since step 3 is so costly to implement, I think it is unlikely that a cryptography-based trading card game will have tradable cards.

Much easier - with each card, store its ownership history. EACH time it is transfered, have it be signed by the previous owner. Originally, the game company signs it as a valid card. On selling it, they record the purchaser's identity (email address, etc)and seal the card with the company key (or set of keys - see above). Repeat as needed. This Message Was Sent With An UNREGISTERED Version Of PMMail. Please Encourage Its Author To Register Their Copy Of PMMail. For More Information About PMMail And SouthSide Software's Other Products, Contact http://www.southsoft.com. ===================END FORWARDED MESSAGE=================== /* From Chris Adams <adamsc@io-online.com> on a Warped PC running a proudly unregistered (for now) PMMAIL 1.5! The Enigman Group - We do Web Pages! */ This Message Was Sent With An UNREGISTERED Version Of PMMail. Please Encourage Its Author To Register Their Copy Of PMMail. For More Information About PMMail And SouthSide Software's Other Products, Contact http://www.southsoft.com.