[145489] in cryptography@c2.net mail archive
Re: A slight modification of my comments on PKI.
daemon@ATHENA.MIT.EDU (dan@geer.org)
Wed Jul 28 23:15:30 2010
From: dan@geer.org
To: "Perry E. Metzger" <perry@piermont.com>
cc: cryptography@metzdowd.com
In-Reply-To: Your message of "Wed, 28 Jul 2010 19:38:40 EDT."
<20100728193840.2e02ea15@jabberwock.cb.piermont.com>
Date: Wed, 28 Jul 2010 22:34:50 -0400
> It is important to remember what we're trying to defend against. As
> many of us have learned through bitter experience, the costs and
> benefits of security systems we deploy are the important part. No one
> needs perfect security in the face of no attackers at all, and even if
> attackers are numerous, if a system has low enough failure/fraud
> rates, no one will complain much.
The design goal for any security system is that the number of
failures is small but non-zero, i.e., N>0. If the number of
failures is zero, there is no way to disambiguate good luck
from spending too much. Calibration requires differing outcomes.
Regulatory compliance, on the other hand, stipulates N==0 failures
and is thus neither calibratable nor cost effective. Whether
the cure is worse than the disease is an exercise for the reader.
--dan
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