[114688] in cryptography@c2.net mail archive
Re: Gutmann Soundwave Therapy
daemon@ATHENA.MIT.EDU (=?UTF-8?Q?Ivan_Krsti=C4=87?=)
Wed Feb 6 13:24:28 2008
Cc: <cryptography@metzdowd.com>
From: =?UTF-8?Q?Ivan_Krsti=C4=87?= <krstic@solarsail.hcs.harvard.edu>
To: Richard Salz <rsalz@us.ibm.com>
In-Reply-To: <OF4C01BFF1.93C582A7-ON862573E2.001273EB-852573E2.0013517A@us.ibm.com>
Date: Mon, 4 Feb 2008 06:25:14 -0500
On Jan 31, 2008, at 10:32 PM, Richard Salz wrote:
> Developers working in almost any field should know the history and =20
> best
> practices -- is PGP's original "bass o matic" any more important =20
> than the
> code in a defibrillator? -- but this is not the way our field works =20=
> right
> now. Compare it to something like civil engineering or architecture.
I think this misses the point. Security is different.
In 2008, I can learn to build pretty good suspension bridges by =20
learning the state of the art of bridge-building. After that, as long =20=
as I live, I run almost no risk of Newtonian mechanics being shown to =20=
be wrong for any value of wrong that would make me go "well, wow, I no =20=
longer understand how to build bridges".
In other words, people who build bridges these days can give you a =20
convincing presentation, based on solid physics and a highly-complete =20=
threat model (soil erosion, material failure, etc) that their bridge =20
will do its job. They can say "this bridge will work because it =20
satisfies well-understood and reasonably immutable laws of nature".
People who attempt to build secure systems have no ultimately well-=20
understood (let alone immutable!) requirements to design against. A =20
good approximation is "a secure system is one that survives all =20
relevant attacks that people in our field have come up with thus far", =20=
but it's clear that a system successfully meeting that goal can simply =20=
cease to meet it any given day. Thus unlike with bridges, you =20
fundamentally can't evaluate the quality of a security system you =20
built if you're unfamiliar with the state of the art of _attacks_ =20
against security systems, and you can't become familiar with those =20
unless you realize that these attacks have each brought down a system =20=
previously considered impregnable. And if by the time you've gone =20
through dozens of broken systems and their corresponding attacks you =20
still think you're smart enough to write a new system by yourself, =20
you're either very brave or very daft.
Neither of those mean you're a bad person, but both mean you shouldn't =20=
be designing security systems.
--
Ivan Krsti=C4=87 <krstic@solarsail.hcs.harvard.edu> | http://radian.org
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