So, if you use the Hybrid Cloud version, does all syncing have to go through the AeroFS servers, or can machines on the same LAN sync directly to each other?
Machines can sync directly in most cases (especially on the LAN, and even over the Internet). If, for some reason, communication cannot be established directly between machines, a relay server is used, but the traffic is encrypted end-to-end between the devices, so the relay server cannot decrypt it or MITM it.
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So, if you use the Hybrid Cloud version, does all syncing have to go through the AeroFS servers, or can machines on the same LAN sync directly to each other?
Machines can sync directly in most cases (especially on the LAN, and even over the Internet). If, for some reason, communication cannot be established directly between machines, a relay server is used, but the traffic is encrypted end-to-end between the devices, so the relay server cannot decrypt it or MITM it.
Take a look here[1] for the security spec
[1] https://www.aerofs.com/security/spec