Bob Smith #45

Public – Private key pairs are used to come up with a shared key, which is then used to encrypt data. So to use PKI, the transmitter (the satellite sending the video feed) has to send multiple copies of the same video feed encrypted with different keys. And, each receiver should be able to talk to the satellite, not just receive data.

I am sure you know public/private key encryption is expensive, so it is used only for initial handshake up until you get a shared key.