Cybercash questions...

[Donald E. Eastlake 3rd]

On Fri, 22 Dec 1995, David Klur wrote:

>      
>      Hello,
>      
>      Just a few questions about Cybercash...
>      
>      - How is the consumer's credit card # stored on his hard drive?  
>      Encrypted with the bank's public key? Or does the consumer have a 
>      private key?

The customer has a private key.  Customer info on their machine is
encrypted under a password.

>      - How does the merchant know where to ship the goods?  Is the merchant 
>      required to ship the goods to the billing address on the cardholder's 
>      credit card account?  If so, does the bank provide the merchant with 
>      this info?  How is it encrypted?  Or does the customer indicate to the 
>      merchant where to ship the goods?  Also, what infor does the merhcant 
>      send to Cybercash, and how is it encrypted?

Billing address establishment is part of shopping.  It need not be
the card billing address.  But the customer needs to enter an
addreess when setting up their credit card. see
	draft-eastlake-cybercash-v08-01.txt
in any of the IETF shadow directories.

>      The fraud possibility I see is that Bob could steal Alice's encrypted 
>      credit card number (by sniffing when she buys something at Charlie's 
>      Internet shop).  Then, without decrypting it, he could use it (still 
>      encrypted) at Don's Internet shop, and ask Don to ship the goods to 
>      Bob's address.  Since Don will not decrypt Alice's card number he will 
>      not know that it is not Bob's card.  Cybercash will validate Alice's 
>      card, but will not know that it is really Bob who is the customer.  
>      Don will ship the goods to Bob, and Alice will get a fraudulent charge 
>      on her bill.

The customer signs the message including the merchant id and order id
before encrypting a bunch of stuff including the credit card number
to send to the merchant.  There isn't anything useful to steal from
the ecnrypted part of that message.

>      Am I missing something?

Donald
=====================================================================
Donald E. Eastlake 3rd     +1 508-287-4877(tel)     dee at cybercash.com
   318 Acton Street        +1 508-371-7148(fax)     dee at world.std.com
Carlisle, MA 01741 USA     +1 703-620-4200(main office, Reston, VA)