[145528] in cryptography@c2.net mail archive
Re: Five Theses on Security Protocols
daemon@ATHENA.MIT.EDU (Peter Gutmann)
Sat Jul 31 18:04:10 2010
From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: cryptography@metzdowd.com, perry@piermont.com
In-Reply-To: <20100731123239.2efc2f51@jabberwock.cb.piermont.com>
Date: Sun, 01 Aug 2010 06:05:38 +1200
"Perry E. Metzger" <perry@piermont.com> writes:
>Inspired by recent discussion, these are my theses, which I hereby nail upon
>the virtual church door:
Are we allowed to play peanut gallery for this?
>1 If you can do an online check for the validity of a key, there is no
> need for a long-lived signed certificate, since you could simply ask
> a database in real time whether the holder of the key is authorized
> to perform some action.
Based on the ongoing discussion I've now had, both on-list and off, about
blacklist-based key validity checking [0], I would like to propose an
addition:
The checking should follow the credit-card authorised/declined model, and
not be based on blacklists (a.k.a. "the second dumbest idea in computer
security", see
http://www.ranum.com/security/computer_security/editorials/dumb/).
(Oh yes, for a laugh, have a look at the X.509 approach to doing this. It's
eighty-seven pages long, and that's not including the large number of other
RFCs that it includes by reference: http://tools.ietf.org/html/rfc5055).
> The signed certificate is completely superfluous.
This is, I suspect, the reason for the vehement opposition to any kind of
credit-card style validity checking of keys, if you were to introduce it, it
would make both certificates and the entities that issue them superfluous.
Peter.
[0] It's kinda scary that it's taking this much debate to try and convince
people that blacklists are not a valid means of dealing with arbitrarily
delegatable capabilities.
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