From: Jeff Weinstein <jsw@netscape.com>
Date: Wed, 31 Jan 1996 04:09:19 +0800
To: cypherpunks@toad.com
Subject: Re: FV Demonstrates Fatal Flaw in Software Encryption of Credit Cards
In-Reply-To: <ad32cd9601021004af4e@[132.162.233.188]>
Message-ID: <310E0D83.111A@netscape.com>
MIME-Version: 1.0
Content-Type: text/plain


Nathaniel Borenstein wrote:
> This is wrong on two main counts:  the ID's are harder to find than
> credit cards, and they're not as directly useful as credit cards.  These
> two facts combine to make the attack more or less irrelevant to FV.
> 
> First of all, the Virtual PIN (FV-ID) is much harder to extract from a
> large data stream because it is arbitrary text, unlike credit card
> numbers, which are self-identifying.
> 
> Second, a Virtual PIN is not a one-way payment instrument, like a credit
> card.  To use FV to buy something on your credit card, you need to
> combine the theft of a Virtual PIN with the compromise of the buyer's
> email account, for confirming transactions.  We all know this can be
> done -- we actually even spell out how to do it in our paper, "Perils
> and Pitfalls of Practical CyberCommerce" -- but it is very hard to
> combine these steps on the large scale that would be needed to mount an
> automated attack, which is the most serious threat to the credit card
> system.

  It would not be much harder than the demonstrated keyboard attack
to create a hacked version of winsock that would implement an
attack against First Virtual.  If the attacker had a list of web
pages that accept FV payments it would be very easy to collect
the ID numbers.  There is no need to attack the large datastream
of keyboard input when the search can be easily narrowed.  Since
FV doesn't use encryption the attack could easily be implemented
in winsock, making it independent of any client software.  A version
that infected the win95 IP stack could be quite effective.  The list
of FV accepting sites would be easily obtainable via a query of
altavista.  Since the infected system is on the internet and has
to periodically send its results to the attacker, it could download
an updated list of FV pages at the same time.  

  Attacking the e-mail verification step of the FV system could also
be accomplished via a hacked winsock.  A bit of POP3 aware code
in the winsock could intercept the verification messages and keep
the e-mail client from ever seeing them.  It could automatically
generate "Yes" responses for all such messages.

  I believe that FV is just as vulnerable to these types of
attacks as any of the encryption based credit card schemes, if
not more so.  The thing that really protects FV is that it can
only be used to buy bit, not real goods, and the bad guys don't
generally care about stealing bits.  This is also what makes FV
not generally useful to people who want to shop over the internet.

	--Jeff

-- 
Jeff Weinstein - Electronic Munitions Specialist
Netscape Communication Corporation
jsw@netscape.com - http://home.netscape.com/people/jsw
Any opinions expressed above are mine.