A way to monitor your files

[Novice.****]

 I am really new to unix and was just wondering if there is a program/file 
 or something ( for lack of better word) that allows me to know when and
 by whom my files have been accessed. I have tried to change the mode of
 the files to limit access to only myself ( at least certain personal files)
 but this measure seems utterly useless with superusers. Encrypting is out
 of the question. Can someone of the pros/experts out there give some info
 on the matter. I would greatly appreciate the help.

 Thanks
 Novice