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 ?