🚀 go-pugleaf

In article <804@n3dmc.UU.NET> johnl@n3dmc.UUCP (John Limpert) writes:

>I read a book on HF radio frequency assignments that said the Department
>of Energy used a scrambler system for the trucks that transport nuclear
>materials.  The system divided the audio spectrum into a number of
>frequency bands and shuffled them around before feeding the audio into
>the transmitter.  The interesting part of the system was the use of some
>sort of key generator to change the mapping at a rapid rate.  I don't
>know how difficult it would be to reconstruct the original signal by
>attempting to match up parts of successive samples.  The nice thing
>about this system was that it worked with conventional radio equipment. 


Yeah, that was the state-of-the-art type of system prior to digital encryp-
tion-of-voice technology. They were, I believe, called "moving band" scram-
blers, or some such. In addition to swapping the various bands around,
about half of the bands were inverted at any given time.

In real-time, this thing was a real pain in the patoozie to defeat, but it
turned out that given a recording, a cryptanalyst (scrambanalyst?) could
extract the voice. It was a slow process, unless the "key" was broken, but
it worked. There were few enough bands (and inversions) that exhaustive
cryptanalysis was quite straightforward.

With modern (cheap) computer technology available to T.C. Mits, I 'spect
these scramblers have become pretty bad juju in the security business. It's
just too easy now (with a computer and a little special hardware) to break
the scramble. I'm not sure, but a also 'spect it can be done more-or-less
in real time these days.


						GO DIGITAL,
						      d


          "In all levels of life, the sheep are only safe
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     Duke McMullan n5gax nss13429r phon505-255-4642 ee5391aa@hydra.unm.edu