[42470] in Cypherpunks
Re: digital cash and identity disclosure
daemon@ATHENA.MIT.EDU (Bill Stewart)
Sat Oct 28 14:51:41 1995
Date: Sat, 28 Oct 1995 11:46:53 -0700
To: tomw@cthulhu.engr.sgi.com
From: Bill Stewart <stewarts@ix.netcom.com>
Cc: cypherpunks@toad.com
At 08:53 AM 10/20/95 -0700, tomw@cthulhu.engr.sgi.com wrote:
>> I don't understand how this could happen? The two coins are identical
>> (as I understood it from the tech backgound of ecash). what has a double-
>> spended coin what a copied single-spended coin not has?
>The process of spending a coin is not simply that of transfering data.
>There is a complicated protocol in which Alice decrypts some of the
>identity information in the coin.
There are several approaches - in the immediate-clearing model,
you can tell if someone's spent coin 111111111111 because the bank keeps
a record of which coins have been spent and refuses to pay anybody
who tries to spend the same coin later; this almost forces you to use
on-line clearing solutions. Chaum's blinding protocols
make it possible for the bank to sign a coin without being able to
trace it to the person withdrawing the coin, so she can spend it anonymously.
Another model uses the protocols Tom described which place a random chunk
of the spender's identity into the coin - one chunk gives away no information,
but two chunks have an extremely high probability of doing so - so you
can go prosecute the guilty double-spender later (or just debit her account
twice...)
Then there are the non-anonymous models.
#---
# Thanks; Bill
# Bill Stewart, Freelance Information Architect, stewarts@ix.netcom.com
# Phone +1-510-247-0664 Pager/Voicemail 1-408-787-1281
#---
