Optical Tempest? I have my doubts...

Tyler Durden camera_lumina at hotmail.com
Thu Jul 17 12:15:28 PDT 2003

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 

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 

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 


>From: Peter Fairbrother <zenadsl6186 at zen.co.uk>
>To: <cypherpunks at 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 
> > soap and water I have wondered just how much you need to protect 
> > circuits from water.  You obviously don't want to allow them to stay 
> > so they corrode, but immersion for a time (up to weeks) followed by a 
> > water rinse and drying might not be so bad.  Do any hardware experts 
> > an opinion?
>A long time ago I used to teach an "intro to computing" class. many 
>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 
>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.
>BTW, do NOT do this with crappy Apple keyboards! They are membrane-based 
>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!
>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 
>key input obviously), and you do learn where the keys are after a while, 
>it's still a hassle.

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