At 09:14 AM 03/10/2003 -0500, Arnold G. Reinhold wrote:On the other hand, remember that the earliest Tempest systems were built using vacuum tubes. An attacker today can carry vast amounts of signal processing power in a briefcase.
And while some of the signal processing jobs need to scale with the target systems,
as computer clock speeds get faster, the leakage gets higher and
therefore shielding becomes harder and leakage gets higher.
Most of the older shielding systems can do fine with the 70 MHz monitor speeds,
but the 3 GHz CPU clock speed is more leaky. Millimeter wavelengths are
_much_ more annoying.
All in all I would not put much faith in ad hoc Tempest protection. Without access to the secret specifications and test procedures, I would prefer to see highly critical operations done using battery powered laptops operating in a Faraday cage, with no wires crossing the boundary (no power, no phone, no Ethernet, nada). In that situation, one can calculate shielding effectiveness from first principles. http://www.cs.nps.navy.mil/curricula/tracks/security/AISGuide/navch16.txt suggests US government requirements for a shielded enclosure are 60 db minimum.
Back when most of the energy lived at a few MHz, it was easy to make enclosures
that had air vents that didn't leak useful amounts of signal. It's harder today.
So take your scuba gear into your Faraday cage with you :-)
One of my pet ideas is to used older, 1990's vintage, laptops for secure processing, e.g. reading PGP mail, generating key pairs, signing submaster keys, etc. They are cheap enough to dedicate to the task, they'd be off most of the time thereby reducing vulnerability, older operating systems and firmware have fewer opportunities for mischief and most viruses won't run on the old software. Easier shielding due to lower clock rate is an advantage I hadn't thought of before.
Basically, if you've got a serious threat of TEMPEST attacks, you've got serious problems anyway...
You could say that about strong crypto in general. Anyone with valuable information stored on a computer has lots to worry about.
Arnold Reinhold
--------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]
