Timothy May wrote,
I don't think all systems must be able to deal with double spending.
For example, the first person to read this number: 45%2)d[12ks&Qmdx and to then submit it any form--in person, by e-mail, via remailer, etc.--to The First Bank of Cyberspace will have $10 sent to him or her, as cash or as a spendable amount of digicash (untraceable to recipient, of course).
I would expect that services might emerge that would strengthen this without the bank getting involved and without loss of anonymity. It might emerge that because of the bank's lack of handling of double spending that in some transactions some payees would request a money order from a trustee. The payee might supply the list of money order suppliers allowed for that day. If the payee does not want the money order addressed with a public key, he can supply a set of alternate keys each encrypted for an acceptable trustee. The money order allows the payee to be as sure that the cash is good as he trusts the trustee (and the bank). With or without the use of a remailer this can add to hiding the payer. However, unless the payee provides a hidden key, the trustee does know who received some payment. The trustee is highly motivated to operate a memoryless system (except for the trustee's own cash) and might be audited to ensure this to both customers and potential physical raiders. The cash bundled in the money order need not be that returned from exchanging the money order payment. Some trustees might return a money order containing cash that has other properties, too. If the payee really trusts the trustee, then no race to exchange the cash is needed--hiding the payee further. The payee can exchange it over a period of time or as needed. Exchange includes indirect exchange as in buying money orders. I'm new to protocols and I mention details below only to add hopefully clarifying material, not to suggest that I have any idea of the right ways to do these things. These can be implemented using PGP. Money Order: The automated trustee checks the money (for money order amount and fee). If it is bad the trustee sends it back. Otherwise, the trustee exchanges the cash and then selects from cash on hand cash of the amount of the money order. This is encrypted for the payee. (The buyer must supply something the trustee would know how to use to encrypt for the payee: public key or message addressed to the trustee containing information on how to encrypt for the payee.) The money is encrypted with that. A description is added to this and it is signed by the trustee and sent back to the payer. The description may or may not mention the payee depending on whether the money was wraped with a public key or not. Escrowed Money Order: The trustee creates a money order that can be opened by either the payer or payee and encrypts that for the escrow agent. A description and signature is added. Generalization: Payees and escrow agents can be abstract recipients such as and/or lists. I wonder how much I could charge for this. Dar =========================================================== Dar Scott Home phone: +1 505 299 9497 Dar Scott Consulting Voice: +1 505 299 5790 8637 Horacio Place NE Email: darscott@aol.com Albuquerque, NM 87111 dsc@swcp.com Fax: +1 505 898 6525 http://www.swcp.com/~correspo/DSC/DarScott.html ===========================================================