Yeah, it would be like satellite TV, with each receiver having a unique key (well, each receiver has a card interface where one can plug in a card with a key. T

Yeah, it would be like satellite TV, with each receiver having a unique key (well, each receiver has a card interface where one can plug in a card with a key. The satellite TV signal sends encrypted decryption keys and as long as you're a subscriber, the chip on your card will be able to decrypt one of those keys, which in turn can decrypt the encrypted broadcast signal. AFAIK originally the DoD weren't thinking of making GPS for public, just for military. Having these requirements would just make it extra complex, and unnecessary. First, it would require a lot of bandwidth, and then yeah, a bottleneck for how many receivers can be deployed, and it could take a lot of seconds until a unit finds a matching key to decrypt. Imagine a soldier needing to wait for her equipment to get the key to find her location while in a firefight...