From: Hal <hfinney@shell.portal.com>
Date: Tue, 5 Apr 94 23:14:21 PDT
To: cypherpunks@toad.com
Subject: Chaum on Traceable Cash
Message-ID: <199404060615.XAA18552@jobe.shell.portal.com>
MIME-Version: 1.0
Content-Type: text/plain


I wrote something last week on whether digital cash should be traceable.
Here is a quote by Chaum in favor of traceable cash.  It is from Eurocrypt 87,
"Blinding for Unanticipated Signatures", on page 228:

"The ability to anticipate a large number of signature types can benefit the
payment system described in [Chaum, D. "Security without identification:
transaction systems to make big brother obsolete," Communications of the
ACM, 28, 10 (Octoboer 1985), pp. 1030-1044].  This would allow customers of
the bank providing a system to each supply a large number of blinded items
when their accounts are opened, without the customers knowing in advance
which particular type of signature will later be applied by the bank.  Not
only can this provide economy of data transfer, but it protects the bank's
customers from being able to (and hence from being coerced into) making
payments that they cannot later trace."

The technical basis for Chaum's statement is obscure, but the political
point is that if you can make an untraceable payment, you could be coerced
into doing so, for example by being robbed at gunpoint.  Contrariwise, if
the cash system used by you and your bank is such that all money is in-
herently traceable, it will be a lot harder to commit robbery, extortion,
kidnapping, and all those other horrors which people fear will come with
digital cash.

Hal