The assumption that inability to get the transmitter or knowledge of how to do it is enough to protect your reciever.
As far as I know, relay satellites also did not use authentication in the past.
I don't think it was a technical limitation and it's likely encrypted uplinks would have been possible long before consumers got encrypted downlinks (subscriber satillite).
The assumption that inability to get the transmitter or knowledge of how to do it is enough to protect your reciever.
As far as I know, relay satellites also did not use authentication in the past.