Securenet/Radio scrambling
Moderator: Queue Moderator
I was wondering what securenet is and how it works. Like why do some PD's go secure sometimes.. why not constantly. Also I was listening to a fed frequency, think it was the FBI and they go "coded". It doesn't sound garbled it just is a squelch and a high tone at the end. Is this something different? Any help is appreciated
A quick Google search gave me the following, it's a pretty good summary:
--Quote--
Instead of sending two-way voice messages as an analog signal, SECURENET first converts the analog voice signal to a digital signal.
Once the signal is in a digital format, SECURENET uses an electronic code key to encrypt, or code, the digital signal. When the encryption is completed, the digital coded message is transmitted.
Receiving radios have an electronic code key that checks for the correct code and then decrypts, or decodes, the message. The radio converts the original digital signal back to an analog voice signal and the listener only hears the intended voice message.
The SECURENET receiving radio can respond to the encrypted call using the same digital encryption process.
With SECURENET encryption, anyone listening in on the channel will hear undistinguishable digital noise. The actual message is undetectable without the proper decoding circuitry and encryption algorithm. SECURENET equipped radios can operate in either the clear mode, for normal voice transmissions, or in the encrypted mode for secure voice transmissions.
--End Quote--
I should add that due to bandwidth restrictions, the resulting audio is of very poor quality, which is why many departments only use it when they have to. This only applies to Securenet with an analog signal. The encrypted Astro digital audio quality is indistinguishable from the unencrypted.
Todd
--Quote--
Instead of sending two-way voice messages as an analog signal, SECURENET first converts the analog voice signal to a digital signal.
Once the signal is in a digital format, SECURENET uses an electronic code key to encrypt, or code, the digital signal. When the encryption is completed, the digital coded message is transmitted.
Receiving radios have an electronic code key that checks for the correct code and then decrypts, or decodes, the message. The radio converts the original digital signal back to an analog voice signal and the listener only hears the intended voice message.
The SECURENET receiving radio can respond to the encrypted call using the same digital encryption process.
With SECURENET encryption, anyone listening in on the channel will hear undistinguishable digital noise. The actual message is undetectable without the proper decoding circuitry and encryption algorithm. SECURENET equipped radios can operate in either the clear mode, for normal voice transmissions, or in the encrypted mode for secure voice transmissions.
--End Quote--
I should add that due to bandwidth restrictions, the resulting audio is of very poor quality, which is why many departments only use it when they have to. This only applies to Securenet with an analog signal. The encrypted Astro digital audio quality is indistinguishable from the unencrypted.
Todd
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Elroy Jetson
- Posts: 1158
- Joined: Mon Sep 03, 2001 4:00 pm
Encrypted audio, though secure from monitoring by unauthorized personnel, has a problem with recovered voice quality. It's not very good, frankly. So it's not used mroe often than it needs to be used, generally speaking.
What you thought you heard, squelch noise followed by a short tone, is actually the encrypted signal. The short tone is the 'end of transmission' indicator. Encrypted signals do sound like noise, and the more efficient the encryption, the more like noise it sounds. Ideal encryption is practically indistinguishable from background noise, and in fact many radios won't unmute on an encrypted signal because it operates the squelch circuit just like background static.
Elroy
What you thought you heard, squelch noise followed by a short tone, is actually the encrypted signal. The short tone is the 'end of transmission' indicator. Encrypted signals do sound like noise, and the more efficient the encryption, the more like noise it sounds. Ideal encryption is practically indistinguishable from background noise, and in fact many radios won't unmute on an encrypted signal because it operates the squelch circuit just like background static.
Elroy
It's not that encrypted audio has a problem with recovery really, it's because Securenet can only sample the analog audio at 12.5 KHz due to RF Bandwidth restrictions. If there weren't the 25KHz channel spacing restriction, it could be sampled at 64KHz (standard sampling rate for "Hi-Fi" analog to digital conversion), and the resulting recovered audio would sound great! Life's not perfect though.
Todd
Todd
Go here, it should answer many of your questions...On 2002-02-23 11:49, CGRESQ192 wrote:
what kind of radios do encryption with the squelch like and tone? And how is it activated
http://www.batlabs.com/encrypt.html
If you're thinking about going down the road that I think you are... save your money.
The Motorola encryption system works on a system of 16 digit/ key characters. It's an 'all or nothing' deal. If you have 15.5 of the 16 digits, you're not going to be able to decode the signal.
This is the beauty of DES/DES-XL.
(yes I know that it is impossible to have a half digit. It was said for emphysis purposes). As for tring to figure out the code... there are 10 numbers and I believe 8 letters. these are generally arranged in a random pattern of letters and numbers. So, for the most part each digit has 24 possible answers. multiply this by 16 positions.
Someone once said that it would take the worlds strongest and fastest computer over five years to break the code. Most agencies will change their code at least once a year. Two years at the most. Also, if battery power is lost for more than 30 seconds, the key is deleted as a security feature.
Enjoy. Good luck.
The Motorola encryption system works on a system of 16 digit/ key characters. It's an 'all or nothing' deal. If you have 15.5 of the 16 digits, you're not going to be able to decode the signal.
This is the beauty of DES/DES-XL.
(yes I know that it is impossible to have a half digit. It was said for emphysis purposes). As for tring to figure out the code... there are 10 numbers and I believe 8 letters. these are generally arranged in a random pattern of letters and numbers. So, for the most part each digit has 24 possible answers. multiply this by 16 positions.
Someone once said that it would take the worlds strongest and fastest computer over five years to break the code. Most agencies will change their code at least once a year. Two years at the most. Also, if battery power is lost for more than 30 seconds, the key is deleted as a security feature.
Enjoy. Good luck.