Digital Cash with dynamic range

Adam Shostack adam at homeport.org
Tue Jan 2 08:30:10 PST 2001


On Mon, Jan 01, 2001 at 12:32:53PM -0800, Ray Dillinger wrote:
| Most of the protocols I'm finding for digital cash don't have much 
| in the way of dynamic range.  Generally, there is a range of values 
| that they are designed for (rarely more than a factor of a thousand 
| or so from smallest to largest) and smaller payments become 
| impossible and larger payments become impractical. 
| 
| The problem is particularly severe for offline protocols, where you 
| can't get the bank online to make change or issue arbitrary-valued 
| coins. 
| 
| Does anyone know any happy exceptions to this rule, where payments 
| ranging from a millionth of a token up through several million  
| tokens could all be practical?  (ie, dynamic range of the twelfth 
| or higher order?)
|
| Anyway, the "practical in arbitrary amounts" assumption is pretty 
| fundamental to useful money.  We achieve it through bank drafts, 
| checks, transfer orders, etc.  But these instruments are not as 
| clear how to do in a digital world where anonymity is preserved. 

"Teller can not make change for bills over $20."
"Visa/MC minimum charge: $15"
"$30 fee for all wire transfers"

So, I don't agree with you that we have a payment system that works
for arbitrary amounts.  Silly laws aside, paying for a multi-million
dollar purchase with cash is irksomely difficult, because
multiple thousands of dollar bills are bulky.  (I'm assuming that
forgery is an important deterrent to having million dollar bills.  I
know I wouldn't want to accept one.)

| In particular, I haven't found low-level details of how the "Mojo" 
| tokens in use by the new MojoNation stuff work. Are they just an 
| implementation of a well-documented protocol, or did they do something 
| new?

I think that the Mojo guys are using un-blinded Chaumian-style cash.
(See Doug Barnes' work on 'identity-agnostic money')

Adam


-- 
"It is seldom that liberty of any kind is lost all at once."
					               -Hume






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