From: "David Klur" <dklur@dttus.com>
Date: Tue, 19 Dec 95 11:59:41 PST
To: cypherpunks@toad.com
Subject: E-cash coin questions (Mark Twain / Digicash)
Message-ID: <9511198194.AA819410227@cc2.dttus.com>
MIME-Version: 1.0
Content-Type: text/plain


     
     
     1.  How many different coins (serial numbers) can the current Mark 
     Twain/Digicash protocol support?
     
     2. Does Mark Twain bank maintain 2 lists: 1 of all the ecash serial 
     numbers for all coins ever produced, and 1 of all the ecash serial 
     numbers for all coins that have been spent before?  Or just 1 list of 
     the spent coins (assuming that any coin that is signed w/MT's private 
     key and does not appear on the "spent" list is still valid and is not 
     counterfeit)?
     
     3.  The Digicash scheme allows each coin to be used only once and then 
     destroyed.  How many coins will it take before all possible coins are 
     minted, used and destroyed thereby requiring banks to issue new coins 
     with "recycled" serial numbers?  Remember, each time a "transaction" 
     takes place, an existing coin is destroyed and a new coin is minted. 
     and a transaction can simply be Alice giving her friend Bob a dollar 
     (not necessarily using the ecash for a purchase)
     
     
     4.  What is the probability of guessing a valid serial number, 
     assuming there are 1 million, 1 billion or 1 trillion coins in 
     circulation?
     
     5.  Suppose you have a very large number of 
cash coins signed by the 
     same bank (say, Mark Twain) and you know the record layout of each 
     coin (easy enough since you can decrypt it with the bank's public 
     key), and for each coin the "bank name" field is the same (because 
     it's the same bank!) -- then, would it be possible to hack the RSA 
     encryption and recreate the bank's private key?
     
     
     -----BEGIN PBP SIGNATURE-----
     Version: 1.0.0, Copyright 1995, Pretty Bad Privacy
     
     David Klur   
     dklur@dttus.com
     
     I am who I am because I say so.  So there. 
     -----END PBP SIGNATURE-------