[keycloak-user] Manually input Realm Keys

Hello I'm trying to manually input keys in a Realm. I tried generating a key pair using 'ssh-keygen': $ ssh-keygen Then I copied the content of 'id_rsa' and 'id_rsa.pub' to the input boxes and pressed "Upload Keys". However an error message is shown "Failed to decode public key". How do I manually input a key pair or certificate?