How to upgrade openssh without disturbing old authentication keys
 

Could you please advise, how we can upgrade the Openssh without disturbing the current keys that are used for password less authentications.

Hi.

The upgrade shouldn't touch the keys as far as I'm aware. If in doubt, copy the /etc/ssh directory somewhere, do the upgrade, test the connection, and if it complains about the authentication just copy the keys back into /etc/ssh

Dave