Update sshd_config

etc/ssh/sshd_config

@@ -1,21 +1,30 @@
 #Port 22
 
+#Prefer ed25519 & ECDSA keys rather than 2048 bit RSA
+HostKey /etc/ssh/ssh_host_ecdsa_key
 HostKey /etc/ssh/ssh_host_ed25519_key
 
+# Allow root access with ssh keys
 PermitRootLogin without-password
+
+# Allow ssh access to some users only
 AllowUsers root
 
+# allow ssh key Authentication
 PubkeyAuthentication yes
 
+# ssh keys path in ~/.ssh/authorized_keys
 AuthorizedKeysFile      %h/.ssh/authorized_keys
 
+# No password or empty passwords Authentication
 PasswordAuthentication no
 PermitEmptyPasswords no
 
+# No challenge response Authentication
 ChallengeResponseAuthentication no
 
-UsePAM yes
 
+UsePAM yes
 X11Forwarding yes
 
 #PrintMotd no
@@ -26,6 +35,7 @@ AcceptEnv LANG LC_*
 # override default of no subsystems
 Subsystem sftp /usr/lib/openssh/sftp-server
 
+# use strong ciphers
 KexAlgorithms curve25519-sha256@libssh.org
 Ciphers chacha20-poly1305@openssh.com
 MACs umac-128-etm@openssh.com,umac-128@openssh.com