-1

we would like to implement a simple security encryption to an RF COFDM signal . this is to prevent any dvb-t receiver to view a channel transmited by air from an ambulance to a station

the RF signal is from a commercial hdmi to dvb-t modulator outputing -6 dbm power .

it is possible to convert RF to a digital signal at 3.3v to be connected to a microprocessor or fpga to be encrypted then converted back to encrypted RF , or decrypted back the same way and getting the original signal ? .

my main question : is there a transceiver that can take a COFDM RF signal and convert it to digital output wich will be encrypted by a separate microprocessor then converted back (using transceiver) to COFDM RF ? . how the transceiver can filter only the broadcasting freqency to be converted to digital ?

also a big problem : lets say we have a 658 Mhz COFDM RF at 8 Mhz bandwith ,if we were able to convert it to a 8 Mhz digital signal and encrypt it wich will lead to a randomized digital signal , can this latest signal be converted to a valid COFDM RF ? like do COFDM need to be applied to a special structure of digital data wich is not the case when we encrypt our signal ?

reforming the question :

COFDM RF(1)=>digital(1)=>digital encrypted(1)=>COFDM RF(2)

now if we go the other way can we get an identical signal to COFDM RF(1) ?

we want to use the most simple encryption to digital signal by applying complementary to bits .

the idea is represented like that

dvb modulator RF =>convert to digital=> encryption=>convert to RF => amp => antenna => air => antenna=>=>convert to digital =>decryption=>convert to RF =>dvb-t STB

if the idea is not possible can we encrypt the hdmi signal instead without modulator complaining ?

  • The RF output of DVB modulator is an analog signal and it cannot be encrypted by digital encryption. Input is digital and can be encrypted, this is how pay TV is implemented. – yyy Apr 20 '18 at 8:37
0

What are you trying to accomplish here? Broadcasting on DVB-T frequencies requires a license in most countries. Your post also makes it sound like your transmitter is intended to be a moving vehicle rather than a stationary site, which is very unlikely to give good performance. Anyone who has tried to use a DVB-T receiver to watch television in a moving car will be able to attest to this. Have you considered using other technologies (possibly 4G) for this?

Your question also mentions ambulances. Depending on where you live the legally required protection for medical data being transmitted over an insecure medium (the air) may also come back to haunt you.

To answer your actual question, no, you cannot (to my knowledge) encrypt an RF signal like this. If you were determined to do this then you would have to demodulate the RF output, encrypt the underlying stream and then re-modulate, which would be quite a bit of effort to go to. I really do suggest that you look at an alternate technology.

  • its licensed ,the boradcasting is mostly done when vehicle is not moving. my main question was : is there a transceiver that can take a COFDM RF signal and convert it to digital output wich will be encrypted by a separate microprocessor then converted back to COFDM RF ? . how the transceiver can filter only the broadcasting freqency to be converted to digital ? – furtsiv Apr 20 '18 at 16:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.