sshd sends its syslog messages using the AUTH facility instead of
AUTHPRIV.  (According to the syslog(3) man page, the use of AUTH is
supposed to be deprecated.)  The result is that sshd messages go into
/var/log/messages and not /var/log/secure.  Since redhat leaves both these
log files readable only by root, the problem is not one of privacy. 
Rather, it is good practice to periodically scan /var/log/secure for
possible breaking attempts, etc,  (it is usually much shorter than
messages).  Not having any ssh entries there is a bad idea, imho.

A simple and immediate fix is to change the entry in /etc/syslog.conf  for
/var/log/secure from

 authpriv.*			/var/log/secure

to

 auth.*;authpriv.*                        /var/log/secure

sshd messages then go into both the messages and secure logs, but that's
ok.  I think that the above change to syslog.conf  is a good idea anyway,
even once sshd's logging gets fixed.