After a couple of days I succeded to start the daemon
Just in case someone else is trying the same, these are the steps:
1.) you generate the keys with ssh-keygen ( actually only rsa key is enough to start the sshd). It generates the keys in home/tc/.ssh/id_rsa folder. If you enter passphrase it will encrypt them.ssh-keygen -t rsa
2.) you start the ssh-agenteval $(ssh-agent -s)
to export the correct env variables.
3.) you add the private key to the agentssh-add id_rsa
4.) inside the config file of sshd_config you must add an undocumented
parameter HostKeyAgent equal to SSH_AUTH_SOCK variable or you will recieve incorrect passphrase errorsudo /usr/local/sbin/sshd -f sshd_config
If everything is ok the daemon must start listening.
Now you can encrypt your private key even better with PBKDF but this is another story.