We have a hosted CentOS 6.5 server in which we have a single user account.  That account has been configured to use SSH keyfile authentication for the users who need to access it.I would like to be able to see which keyfile was used to authenticate each login; effectively telling me which end-user logged into the single unix user account.  Is there a mechanism for doing so?
How can I determine which SSH keyfile was used to authenticate a login?
ssh;logs;authentication;key authentication
On CentOS there is /var/log/secure. This holds the fingerprints of the logins: Aug  7 23:12:57 my-server sshd[2584]: Accepted publickey for user from 192.168.1.156 port 58279 ssh2: RSA 32:f1:aa:aa:aa:aa:aa:aa:bb:be:ef:c3:aa:bb:cc:f8Map these back to the keys and you have the info you need.You can get the key fingerprints by doing:ssh-keygen -l -f ~/.ssh/*.pub