We have discovered an issue where adding an SSH key via the Project Settings → SSH Permissions menu will fail with the following error when the SSH key has been generated via ssh-keygen with the default settings on macOS Mojave:
It looks like this private key is invalid.
Please check if you have pasted the right key.
This happens because CircleCI currently doesn’t support OpenSSH-style keys. Please generate a PEM key with the following command instead:
ssh-keygen -t rsa -b 4096 -m PEM
Thanks to the author of the answer here and the author of the idea here for the workaround.