The ssh application uses the Erlang applications public_key and crypto to handle public keys and encryption, hence these applications needs to be loaded for the ssh application to work. In an embedded environment that means they need to be started with application:start/[1,2] before the ssh application is started.
The ssh application does not currently have an application specific configuration file as described in application(3), however it will by default use the following configuration files from openssh: known_hosts, authorized_keys, authorized_keys2, id_dsa and id_rsa, ssh_host_dsa_key and ssh_host_rsa_key. By default Erlang SSH will look for id_dsa, id_rsa, known_hosts and authorized_keys in ~/.ssh, and the host key files in /etc/ssh . These locations may be changed by the options user_dir and system_dir. Public key handling may also be customized by providing a callback module implementing the behaviors ssh_client_key_api and ssh_server_key_api.
id_dsa and id_rsa are the users private key files, note that the public key is part of the private key so the ssh application will not use the id_<*>.pub files. These are for the users convenience when he/she needs to convey their public key.
The known_hosts file contains a list of approved servers and their public keys. Once a server is listed, it can be verified without user interaction.
The authorized key file keeps track of the user's authorized public keys. The most common use of this file is to let users log in without entering their password which is supported by the Erlang SSH daemon.
Currently rsa and dsa host keys are supported and are expected to be found in files named ssh_host_rsa_key and ssh_host_dsa_key.