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Showing posts from March, 2015

Voice inversion with GNU radio

Voice inversion is security through obscurity. It is an analogue way to obscure transmission content.

There are all kinds of variations of this scrambling, offering different levels of security. The general idea is they take a signal and as the name recommends - inverts it. Meaning low frequencies become high and vice versa.

This scrambling is a pretty old technique. It prevents people from just listening in. Nowadays with fancy software and computers it is pretty obsolete. IT IS OBSOLETE *cough*Elion*cough*.

Software has been floating on the internet a long time, probably used by HAM radio operators. Basic rule is that you take the output from the radio receiver and pipe it to the computer. Computer with its magic outputs it as human understandable information. Now ,for example, it is useful to use a SDR.


Wikipedia suggests:

In the simplest form of voice inversion, the frequency "p" of each component is replaced with "s-p " , where "s"  is the fr…