[Cryptography] Why prefer symmetric crypto over public key crypto?

Jeffrey I. Schiller jis at mit.edu
Mon Sep 9 14:48:56 EDT 2013


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Just to throw in my two cents...

In the early 1990’s I wanted to roll out an encrypted e-mail solution
for the MIT Community (I was the Network Manager and responsible for
the mail system). We already had our Kerberos Authentication system
(of which I am one of the authors, so I have a special fondness for
it). It would do a fine job of helping people exchange session keys
for mail and everyone at MIT has a Kerberos ID (and therefore would
permit communication between everyone in the community).

However, as Network Manager, I was also the person who would see legal
requests for access to email and other related data. Whomever ran the
Kerberos KDC would be in a position to retrieve any necessary keys to
decrypt any encrypted message. Which meant that whomever ran the KDC
could be compelled to turn over the necessary keys. In fact my fear
was that a clueless law enforcement organization would just take the
whole KDC with a search warrant, thus compromising everyone’s
security. Today they may well also use a search warrant to take the
whole KDC, but not because they are clueless...

The desire to offer privacy protection that I, as the administrator,
could not defeat is what motivated me to look into public key systems
and eventually participate in the Internet’s Privacy Enhanced Mail
(PEM) efforts. By using public key algorithms, correspondents are
protected from the prying eyes of even the folks who run the system.

I don’t believe you can do this without using some form of public key
system.

                        -Jeff
–
_______________________________________________________________________
Jeffrey I. Schiller
Information Services and Technology
Massachusetts Institute of Technology
77 Massachusetts Avenue  Room E17-110A, 32-392
Cambridge, MA 02139-4307
617.910.0259 - Voice
jis at mit.edu
http://jis.qyv.name
_______________________________________________________________________



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