In order to test a use case I installed syncthing on two computers and two smartphones :
A. EndeavourOS > syncthing v1.22.0 “Fermium Flea”
B. Ubuntu 20.04 > syncthing v1.22.0 “Fermium Flea”
C. Oppo Find X 3 Lite Android 12 > Syncthing v.1.21.0
D. Samsung A3 (2017) Android 8 > Syncthing v.1.21.0
The idea is to use my smartphones as bridges to sync multiple computers (that are in various locations).
C. would allow syncing a folder “ClearSync” containing non-sensitive data (i.e. data which is visible/not encrypted on C.)
D. would allow syncing a folder “sync” containing sensitive data (i.e. data which is encrypted/not visible on C.)
I tested to sync A. and B. through C. It worked perfectly (I tested to sync both encrypting “ClearSync” on C. and not encrypting it).
The issue came from D. I was unable to sync A. or B. with D. I tried to sync both both encrypting “Sync” on D. and not encrypting it and I always have the same error message :
Failure checking encryption consistency with device Samsung A3 (2017) for folder “Sync” (abcde-vwxyz): remote expects to exchange plain data, but local data is encrypted (folder-type receive-encrypted)
On D. the receiving folder is located on a 64Go SD card (I don’t have enough internal memory). I tried with an encrypted SD card and with a not encrypted SD card and it didn’t change anything…
The error message has nothing to do with encrypting the SD card (or any other storage) that uses encryption built into the OS. It’s about untrusted/encrypted devices in Syncthing. Please check https://docs.syncthing.net/users/untrusted.html if you haven’t already.
Basically, if you share a folder protected with a password, then the other side must add the folder as “Receive Encrypted”. Then, if you want to share that “Receive Encrypted” folder from the second device with yet another device, then that third device also needs to either add it as “Receive Encrypted” again, or you can input the password that was originally set on the first device, which will allow the third device to sync the data decrypted.
Just a side note, but if those are your own devices and you encrypt the local storage already, then there’s normally no real need to use encrypted folders in Syncthing, as access to the data is already limited to just one person, i.e. yourself.
You’re right it doesn’t seem to be linked with the sd card, since when I pick a folder from internal storage I have the same Issue.
I don’t understand why I have this issue since with the same config everything works well with C but not with D. The only difference is the Android version.
I wanted to encrypt sensitive data on D because smartphones can easily be stolen or lost.
Anyway even without encryption I am not able to sync with D. Neither A to D, nor D to A, nor D to B, nor B to D work…