Parties and roles

We will use the following terminology for the parties involved in VarietyCash. In a typical transaction there would be three parties involved: the payer, the payee, and the bank or e-money server. However, we would like to be more specific than that:

• Participant - A generic name for a party involved in the system.
• Issuer (${\em I}$) - Party who issues coins.
• Coin-holder (${\em CH}$) - A party who holds coins or has the potential to do so.
• Payee (${\em PY}$) - A party who is willing to accept coins as payment (e.g., a merchant).
• Bank (${\em B}$) - A number of banks will be involved in moving funds due to conversions between electronic and real money.
• Certification Authority (${\em CA}$) - The party who can ``certify'' the public keys of the participants. (In some scenarios, this role can be played by the Issuer itself.)

In turn, a coin-holder may play the following roles:

• Coin Purchaser (${\em CP}$) - purchases coins from issuer
• Redeemer (${\em RD}$) - turns coins into real money
• Payer (${\em PA}$)- customer who pays for goods/services with coins
• Refresher (${\em Rf}$) - gets new coins for old
• Changer (${\em Ch}$) - makes change

Further, we make the following distinction amongst participants:

• Registerer (${\em RG}$) - Register a public key at the issuer
• Enroller (${\em EN}$) - Enroll for a particular role such as coin purchaser or merchant

The idea here is that a participant may wish to be able to ``play the game,'' i.e., accept and use coins as a form of payment, without going through the more elaborate process that enables the purchase or redemption of e-money. Note that parties and roles are not mutually exclusive.

In VarietyCash all the participants have distinct identities, as well as public keys. The issuer has a database listing the identities of all participants, and, for each one, its public key. This information is entered at the time of registration. In all transactions directly involving the issuer, there is thus no need for an external certification authority; however, the design leaves an option for such a case.

We assume in this extended abstract a unique issuer, thus dispensing with the presentation of a more elaborate clearing system.