Micropayments, redux

[Zully Ramzan]

It appears that while probabilistic polling (combined with Payword) and the Peppercoin schema have some structural similarities, the underlying purpose of using probabilities is different.  In particular, Peppercoin/Lottery utilizes probabilities to determine whether or not a user will be charged (which indirectly sets the value of a given coin).  In the probabilistic polling schemes, on the other hand, it seems that the vendor always "charges" the user (but often without knowing whether or not the user has exceeded his or her spending limit); that is, the goal, in this case, appears to be to thwart overspending of a given digital coin.  

One might try to argue that at a more fundamental level these two uses of probabilities are, in some sense, equivalent -- but even if that's the case, I still don't think that the connection here is obvious.  The lottery scheme is a paradigm shift in electronic payments since the end user doesn't always get charged, which is initially somewhat counterintuitive.   

I believe that the lottery ticket scheme was originally presented in the rump session of the same conference (Financial Cryptography '97) as the probabilistic polling scheme (and both are published in the same conference proceedings).  

Regards,

Zulfikar Ramzan
 


-----Original Message-----
From: Andrew Odlyzko [mailto:odlyzko at dtc.umn.edu]
Sent: Monday, December 16, 2002 8:13 PM
To: cryptography at wasabisystems.com
Subject: Re: Micropayments, redux


The Micali-Rivest Peppercoin scheme <http://www.peppercoin.com>
seems awfully hard to distinguish from an instance of the
probabilistic polling scheme invented by S. Jarecki and myself,
which was presented at the first Financial Cryptography conference
in 1997, published in "Financial Cryptography," R. Hirschfeld, ed., 
Lecture Notes in Computer Science #1318, Springer, 1997, pp. 173-191, 
and is available online at

   <http://www.dtc.umn.edu/~odlyzko/doc/polling.pdf>

and

   <http://www.dtc.umn.edu/~odlyzko/doc/polling.ps>.

(This scheme is also covered by US patent #5,999,919.)

Andrew

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