On Dec 18, 11:46 pm, (George Orwell) wrote:
Back in the 60s or 70s, I used to hear US military chats around
8megacycles. Nothing interesting as I recall, except once when one of the
people said 'go to green' and the transmissions were suddenly encrypted.

The encryption seemed like it was the kind of thing where the voice
spectrum is broken into segments and the segments moved around.

It must have been, even then, a low-level code, since anyone with a
serious computer for the time (corporations or governments I would
guess) could have unscrambled it.

Does anyone else remember, or still hear, these kinds of non-digital voice
codes?

Il mittente di questo messaggio|The sender address of this
non corrisponde ad un utente |message is not related to a real
reale ma all'indirizzo fittizio|person but to a fake address of an
di un sistema anonimizzatore |anonymous system
Per maggiori informazioni |For more info
https://www.mixmaster.it

By the late 60's or early 70's these FDM systems were being replaced
by the first digital units.
I meet a guy who was a high level state department data geek and we
were discussing 'voice
scrambling'. He said the first generation of digital scramblers had
some serious issues.
They were two part devices. First a hardware codec then a hardware
with software key encryption.
The codec was built by TRW and worked great, but only for English.
French and German would
not get encoded correctly and even English with strong accents was
problematic. The way that
system worked was connect analog, switch to digital then enable
encryption. He said a great
number of people were upset when step 2 failed. TRW hired some
linguists to solve the problem
and within 90 days a much better codec was developed that allowed for
much greater compression.
The basic encryption engine is still similar and older units will
interoperate with the newest units
for some levels of security.

Some where on line there is a repository of the output of the various
voice encryption systems
used since WWII. During the 'big one' the US and the Brits used
single band voice inversion.
We underestimated both the German skills and the fact that people can
learn to understand
single inverted speech.

I will search my bookmarks to see if I saved the link. It was
fascinating to hear the different schemes
used by the various governments and private companies, Several
companies had much better
systems then either us or the USSR.

Terry