Canon EOS R3 Advanced User's Manual page 688

Importing a root certificate for FTPS
If you specified [FTPS] FTP mode when configuring connection settings, the root certificate
used by the FTP server must be imported to the camera.
Only the root certificate with a file name of "ROOT.CER," "ROOT.CRT," or "ROOT.PEM"
can be imported to the camera.
Only one root certificate file can be imported to the camera. Insert a card containing the
root certificate file in advance.
The priority card selected for [Record/play] or [Playback] in [ : Record func+card/
folder sel.] is used to import a certificate.
It may not be possible to trust servers you try to connect to in FTPS connections with a
self-signed certificate.
1.
Select [
2.
Select [Connection option settings].
3.
Select [FTP transfer settings].
: Network settings].
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