I am able to SSH into an Embedded Linux device remotely using a private key with the following command as example (where id_rsa is the private key file):
ssh -i id_rsa firstname.lastname@example.org
This will be authenticated on the device using the matching public key stored on the device.
What i'm wondering is, must a private key be used like when authenticating via SSH this way, or should vice-versa also work? hence private key on the device instead , but public key used in the SSH command to access the device?