Re: NSA chooses ECC

From: Michael Amling (nospam_at_nospam.com)
Date: 10/30/03 

Date: Thu, 30 Oct 2003 18:03:39 GMT

John Hairell wrote:
>
> The caveat is that the laser transmitter/receiver has to be at right
> angle to the window being lased. The laws of optics still prevail.

   Wouldn't it be sufficient if the light from the transmitter reached
the receiver along two paths, one of which bounced off the window and
the other of which was of constant length? The receiver could be in a
different building and at a different height from the transmitter. The
interference between two such paths would surely be sufficient if their
lengths differed by less than the coherence length of the laser.
   Granted, normal incidence would make the easiest reading. As the
angle of incidence departs farther from the normal, the difference in
light path length as a function of window surface displacement decreases.

> Also, white noise deliberately added to the window surface can act as
> a countermeasure, although advanced signal processing can still allow
> speech recovery.

   What you want is one of those noise cancellers set up to cancel the
conversation.

> There also exist laser sensors that detect the
> radiation from a snooper.

   Angles farther from the normal would reduce laser radiation going
through the window to a detector. Away from the normal, using TM
polarization might help since TE polarization at Brewster's angle has no
reflection at all.

--Mike Amling

Relevant Pages

  • A REAL TIME TRAVEL MACHINEn ATTEMPT
    ... Here is a basic layout of the window type of travel machine. ... Take a large silicon wafer, ... Define the correct revloving and angle of laser. ...
    (sci.physics)
  • Re: Strange question.
    ... But when the angle is not strait, ... Draw a ray from your eye to the sun. ... the window was not perfectly facing ...
    (rec.photo.digital.slr-systems)
  • Re: WEIRD problem with CD player
    ... Apparently the electronics need feedback from the laser to tell it ... Shouldn't the laser itself be moving by the coils ... If it is flat or tipped to any angle front to back, the spindle motor ...
    (sci.electronics.repair)
  • Re: The Price is Right?
    ... the valves on my KZ1000P and the tried helicoiling a few of the bolt holes ... angle too. ... It was at that point that the swear jar ... The window part, as best I can recall, ...
    (rec.motorcycles)
  • Re: Applied Trig
    ... Mounted on the plane is a laser, ... nose of the airplane is aligned with the +x axis. ... I want to know how to factor in the angle of pitch and bank to get the ...
    (sci.math)
Loading