--- message 1 ----
> From: Tim May [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, March 07, 2000 4:03 PM
> Subject: RE: About payee untraceability ...
> ...
> Payer untraceable cash plus payer untraceable cash in the
> other direction becomes mutually untraceable cash. How else
> could it be?
> ...
--- message 2 ----
> From: Tim May [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, March 07, 2000 4:23 PM
> Subject: RE: About payee untraceability ...
> ... By the way, to forestall Clarice unblinding the cash received
> from Dave and thus knowing the identity of the cash Alice gets,
> here's one option:
>
> Alice provides the appropriate keys in an envelope Clarice
> encrypted to Dave, such that Dave encrypts the blinded cash
> he sends back to Clarice. Clarice cannot ever unblind this
> cash herself, as its locked in an envelope only Alice can
> open.
You cannot (a)buse my system(s) in this manner. The account that
the payee will be able to deposit the money in is the account that
is specified by the payer in his/her signature when making the
payment. If payer-only untraceability is switched on in the design,
the payee cannot prevent the payer's device(s) [user-controlled
computer / smartcard] from learning the account to which the money
can be deposited. That is, payer untraceable cash plus payer
untraceable cash in the other direction does NOT become mutually
untraceable cash.
As to your argument that there need be only one payment system in
the world with two-sided untraceability:
- the fact that a crime is *possible* does not mean one might as
well facilitate it.
- your "extortion solution" requires the victim to perform fairly
extensive things, such as perhaps show up in another country in
person. What I am more worried about in a fully untraceable ecash
system is if anyone can extort other people for much smaller
amounts by threatening to divulge certain info about them or
to trigger a logic bomb or the like. *That* is why I think a
large-scale electronic cash system with 2-way untraceability
may not be acceptable to anyone including consumers.
Stefan
