Notice: during the installation of FreeBSD, I enabled sshd.

Configuration

# cp /etc/ssh/sshd_config /etc/ssh/sshd_config.org
# vi /etc/ssh/sshd_config
PermitRootLogin no
RSAAuthentication yes
PubkeyAuthentication yes
PasswordAuthentication no
PermitEmptyPasswords no
ChallengeResponseAuthentication no
AllowUsers yourUserName

Key generation

% mkdir ~/.ssh
% chmod 700 ~/.ssh
% cd ~/.ssh
% vi ssh-key.pub
yourPublicKey
# ssh-keygen -i -f ssh-key.pub > authorized_keys
# chown yourUserName:yourGourp authorized_keys
# chmod 600 authorized_keys
% rm -f ssh-key.pub

Confirmation

# /etc/rc.d/sshd restart
% netstat -a | grep LISTEN
tcp4       0      0 *.ssh                  *.*                    LISTEN

OK, now I can connect this computer by SSH with private key and its password.