From: iang@cs.berkeley.edu (Ian Goldberg)
Date: Thu, 23 May 1996 05:38:31 +0800
To: cypherpunks@toad.com
Subject: Re: Is Chaum's System Traceable or Untraceable?
In-Reply-To: <v02140b0aadc66b47f5b3@[206.170.39.104]>
Message-ID: <4nvdgd$4ll@abraham.cs.berkeley.edu>
MIME-Version: 1.0
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In article <v02140b0aadc66b47f5b3@[206.170.39.104]>,
Tim Dierks  <tim@dierks.org> wrote:
>Not that full anonymity isn't a Good Thing, but couldn't this be solved by
>having the merchant (who presumably is on-line) provide PDA <-> mint
>connectivitiy for the purposes of getting change, exchanging coins, etc.?
>My assumption is that all the ecash protocols are not subject to a MITM
>attack, which I would just presume to be good practice.

But if you go online, you give away your identity due to a timing coincidence.
>
>Also, given the fully anonymous protocol as you've described it (both payor
>and payee blind the coins), what's to prevent the merchant from depositing
>your change before he gives it to you? Unless your PDA is online, you'll be
>home before you find out the hot dog vendor shorted you. (It's my
>understanding that the current digicash system does not support Chaum's
>method of revealing the identity of double-spenders).

That's another of the cool features of the "anon" protocol: the coin isn't
complete until the protocol is finished.  The hot-dog vendor doesn't have
enough information to spend the coin.

   - Ian

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