I want to use the PI for a commercial data logging device that reports the data back to a cloud based server via the internet. There will potentially be thousands of PI's that are physically installed at unsecure sites (like people's homes.)
I will secure all ports on the PI except SSH, and connect to it using SSH-Key authentication only. The PI itself will then use SSH-Key authentication to connect to the server to upload it's data.
As people have physical access to the device, they could remove the SD card from the PI and look at the SSH key for the server, and the server ip address etc.
How can I stop someone from getting the keys to my cloud based server from studying the SD card contents?