The fact that the embassy talks to the mothership is not secret.
How much it does so might be, and what it talks certainly is, but that's easily fixed by getting a line with dedicated bandwidth, running an encrypted connection (VPN or something custom) over it, and padding the traffic to ensure the bandwidth usage is constant (if you have a 100 Mbit line and 10 Mbit of traffic, you send 90 Mbit of padding).
The keys for the VPN get delivered via diplomatic courier.
How much it does so might be, and what it talks certainly is, but that's easily fixed by getting a line with dedicated bandwidth, running an encrypted connection (VPN or something custom) over it, and padding the traffic to ensure the bandwidth usage is constant (if you have a 100 Mbit line and 10 Mbit of traffic, you send 90 Mbit of padding).
The keys for the VPN get delivered via diplomatic courier.