GPG PGP S/Mime vulnerability
Tue Aug 7 11:10:02 2001


I agree to all of your comments on this, it is true that a
'real' signatures offers no better security.

But, at least in my country, the governement wants to make
digital signatures legally binding.
In my country (Belgium b.t.w.), they would probably go for
S/Mime...  According to them, you should be able to sign orders,
cheques and every other thinkable transaction using such a
signature.  These signatures would be legally BETTER than your
written one!

I know the example 'you're fired' was very badly chosen.  But
let's say you order something by e-mail, and someone, just to
bug you, resends your order (with a valid signature), would mean
that you have two legally binding orders outstanding... instead
of the one you wanted...

I know, he/she can't really gain from it, but people seem to be
intend on using new technologies (like e-mail), just to harm
Who hasn't been hasseled yet by anonymous e-mails, using the
lack of authentication in mail sending protocols?
I personally was bugged by racists for about a year through high
school because my girlfriend in those days was Turkish (we're
married now).

What I'm afraid of is that, with the current implementation,
digital signing will go the same way as so many other protocols...

That's just my two cents...

Kind regards



The solution to this is the same as with physical
signatures: do not sign ambiguous documents!

You would never sign a document saying "I sell my house to you",
you would only sign something like "I, Joe Smith, sell my
house, 123 Main St., Nowhere PA, to Jane Doe for $150,000,
effective 1/1/2001".

BTW, no one with any common sense would trust such an
ambiguous document as "You're FIRED!", even if it was 
signed. There is no evidence at all that it was addressed
to the recipient - it's just too ambiguous.

Similary with the "I sell my house to you": no court would
even consider it - it's just too ambiguous.

With the best technology, we still need common sense
on both ends of the communication channel. 

-----Original Message-----
From: Guy Van Sanden
To: GnuPG Users
Sent: 8/3/2001 6:47 AM
Subject: GPG PGP S/Mime vulnerability

I've read through Don Davis' whitepaper about the disadvanteges
of the 
current sign (and encrypt) features in all common standards to
do so.

His basic reasoning (and I've tried it, it works!) is:
I send a signed message to someone stating "you're fired".  He gets 
angry and decides to get even with another collegue...
Using SMPT he puts my address in the from header, then pastes the 
entire source of my signed message to him in the body (including
signatures), and sends it of to someone else...

That last person opens a message, which he thinks comes from me,
trusts the contents because the signature is verified!

More info is over here:

Kind regards