I dunno...I'm thinking that optical tempest is probably bullshit 99% of the time, but what do I know? My Optical specialities are ultrafast and optical networking. But I still don't believe that specular reflection of smallish type from a monitor will have anything that is recoverable. Of course, this is going to be dependent on the quality of the wall material, but for most not-so-even plaster/drywall painted surfaces, I just can't believe the appopriate spacial frequencies of the image are not scattered after that kind of reflection. The conspiracy theorist is telling me there's some reason they floated the optical tempest story, though I can't quite figure out what that reason is... -TD

From: Peter Fairbrother <zenadsl6186@zen.co.uk> To: <cypherpunks@lne.com> Subject: Re: Security for Mafiosos and Freedom Fighters Date: Thu, 17 Jul 2003 12:12:12 +0100

Bill Frantz wrote:

...

Ever since I heard that manufacturers were cleaning assembled boards with soap and water I have wondered just how much you need to protect electronic circuits from water. You obviously don't want to allow them to stay damp so they corrode, but immersion for a time (up to weeks) followed by a fresh water rinse and drying might not be so bad. Do any hardware experts have an opinion?

A long time ago I used to teach an "intro to computing" class. many students were older people who were afraid to physically touch a keyboard - partly just because it was unfamiliar, because it meant they were actually, now, starting on the road to learning, because they feared to "break something", or because they thought they might get a shock (I kid you not). I digress.

One way of making them feel more comfortable was to "accidently" spill a drink on a keyboard, than immerse it in a sink, rinse, and hang out to dry. Sometimes I used a hairdrier to reuse the keyboard during the lesson, but mostly I just left it overnight to dry. That gave some at least of them some confidence that it was ok to touch the keyboard.

I've also washed an iMac (which had fallen in the sea) by immersion in tap water and careful drying, the CD needed more care (drying with IPA), I took out the hard drive first and was careful with that, also cleaned all connectors with solvent cleaner, but it worked ok afterwards.

<peeve> BTW, do NOT do this with crappy Apple keyboards! They are membrane-based and will be destroyed. They are also hard to open for repair, and when I asked an Apple chap about them he said "You should never drink near a keyboard". What crap! </peeve>

I give no guarantee that it won't destroy your keyboard, but it won't hurt most keyboards.

-- Peter Fairbrother

BTW, m-o-o-t uses a randomised virtual keyboard with TEMPEST (both EM and optical) resistant fonts. It's okay for inputting keys, but it's a hassle for inputting text.

Which means that your keys might be safe from keyloggers (both hardware and software), but your plaintext isn't. Sigh. I'm trying to improve it by putting the "senhorita" letters in one block and the rest elsewhere (not for key input obviously), and you do learn where the keys are after a while, but it's still a hassle.

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