I can generate a valid key file for my Mosquitto setup that fails the minimum size check of 128, for example this kind of key: -----BEGIN PRIVATE KEY----- MC4CAQAwBQYDK2VwBCIEIFXWXY9yVJRKhZRfLz/oaAcjmOzX/2El+QRU+/1Npyfe -----END PRIVATE KEY-----