From: Bill Stewart <stewarts@ix.netcom.com>
Date: Mon, 18 Aug 1997 03:01:38 +0800
To: "Mark M." <markm@voicenet.com>
Subject: Re: Getting ecash without an MTB account
In-Reply-To: <Pine.LNX.3.95.970815101917.1090E-100000@www.ctrl-alt-del.com>
Message-ID: <3.0.2.32.19970817112235.030651c4@popd.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



At 03:15 PM 8/15/97 -0400, Mark M. wrote:
>There are two ways of handling the double spending problem.  One is online
>clearing where the bank keeps a database of all deposited coins.  
.....
>The other protocol is very complex and involves an interactive protocol
>to reveal one half of the payer's identity which is split using a simple
>XOR.  When a coin is double spent using this protocol, the payer's identity
>is revealed.  I don't know if this protocol can be used for double-blinded
>coins, but even if it could, there wouldn't be many advantages over
>online clearing.

The advantage is that it doesn't need to be online, and being online
is sometimes inconvenient, and sometimes increases your transaction costs.
For some applications, such as wallets, being online means trusting the
telecom facilities provided by the person you're exchanging money with,
which also requires more protocol support.

There is another approach, which is the observer stuff from Stefan Brands,
or whatever he's working on these days, using some sort of "trusted" 
processing component in the wallet to prevent double-spending.


#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts@ix.netcom.com
# You can get PGP outside the US at ftp.ox.ac.uk/pub/crypto/pgp
#   (If this is a mailing list or news, please Cc: me on replies.  Thanks.)