March 24, 2008

S/MIME: we don't need more reasons why it failed...

Reading up on econ and sec for something that won't be mentioned in this post, I stumbled across this passage by Ozment and Schechter in "Bootstrapping the Adoption of Internet Security Protocols":

If Alice has adopted authentication, she signs all of her email. She thus expects Bob to reject unsigned messages that purport to be from her but cannot be authenticated. If Alice has not adopted authentication, she does not sign her messages. She thus expects Bob to accept messages from her even though they are not signed. To know whether to accept an unsigned message purportedly from Alice, Bob must know whether Alice has adopted authentication.

That's as eloquent a comment as I've come across of what we might call the S/MIME signing problem (with some hints to other systems like OpenPGP or SSL).

The authors then spend another 12 or so pages addressing the issue, and I've yet to read that, but it does seem that we can shortcut their analysis and say: this market won't work! Here's more:

Solving this problem requires a secure mechanism through which Bob can determine if Alice has adopted authentication. For example, if Bob already knows Alice he might consider it safe to call and ask if she signs her messages. Unfortunately, the Internet has lacked a general mechanism with which to securely determine whether a system or its users has adopted an authentication technology.

Students of tautology will find that interesting. What to do? From my podium, I say this:

There is only one mode, and it is secure.

The 3rd hypothesis has the legs to walk this journey, and it would carry S/MIME into securing much more email, if only those legs were set free to walk your secure talk. Now to read the rest of their paper...

Posted by iang at March 24, 2008 04:20 PM | TrackBack
Post a comment

Remember personal info?

Hit preview to see your comment as it would be displayed.