deinvert: A Voice Inversion Descrambler

Voice inversion scrambling is a simple and old security method used on analog radios to try and obscure conversations from being listened in on by people with scanners. It works simply by by moving the low frequencies higher and the high frequencies lower, or in other words inverting the audio. A descrambler is then required to recover the true audio, otherwise you will only hear garbled audio. Voice inversion provides little real security, as it is very simply to descramble, and many scanner radios already have descrambling features built in. These days most secure communications are digital and encrypted, but voice inversion scrambling is still available on many analog radios, and could still be in use by some users looking for protection against casual eavesdroppers.

Oona Räisänen (aka windytan) has recently released a simple program called ‘deinvert’ over on GitHub. This program is a descrambler that reads in a scrambled wav file and outputs a descrambled audio file. The audio file could be easily recorded with an RTL-SDR and rtl_fm, or a similar SDR.

Way back in 2013 she also did a post on her blog about voice inversion scrambling which is a good read for further information on how it works, and how to descramble it.

Voice Inversion Scrambling Spectrograph Example
Voice Inversion Scrambling Spectrograph Example

3 comments

  1. Dave NF2G

    “…many scanner radios already have descrambling features built in.”

    One AOR model does. There might be one or two others. But anything that can defeat any form of scrambling or encryption cannot be manufactured, marketed or sold in the United States (where the vast majority of the scanner market exists). The two big scanner manufacturers – Uniden and Whistler – do not include voice inversion in their models.

    • Kandi Klover

      Get over yourself autistic ham loser. No one cares and they can easily be bought in the USA and people do all the time. In addition you don’t have to get an AOR (which has multiple units capable of this) but just a cheap chinese commercial radio and tune in with the scramble feature enabled. Useless manchild moron. This is why you’re joke of a self important hobby is dead. Outdated old crybaby.

      • DaveNF2G

        Wow. Took you a whole year to become incensed enough to toss the insults. I wonder who really has the handicap here.

        I understand that in the 21st Century, wrong is the new right. I was not attempting a judgment in my comment but stating facts. If you don’t like the facts, that is your privilege, but the universe doesn’t operate according to what we feel or want.

        You have a right to your opinion. That comes with the right to be wrong occasionally.

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