Anyone around here know details on the encryption used by Galileo, Beidou, and GPS? Google does not turn up much. It would be interesting to hear about how they

Anyone around here know details on the encryption used by Galileo, Beidou, and GPS? Google does not turn up much. It would be interesting to hear about how they're doing this. With the constraints that they have (receivers not necessarily always online to receive key updates, extremely low bandwidth to work with, systems depend heavily on this information, fast locks are important) it would not surprise me if the encryption scheme has big holes in it. On the other hand, some of these constraints can be dealt with by making receivers fall back to the unencrypted signal until they're locked long enough to get their new keys. And given that this is military, they might err on the side of security rather than accessibility. So who knows.