best way to check for modification of self

[klaus@mail.lds.loral.com (Christopher Klaus)]

I am looking for C src or algorithms that would be useful for a program
to check its own integrity and make sure it hasnt been modified.  

Looking at the filesize of the file would not help, since I want to make
sure no one has modified just some text, etc.  I would like the algorithm
or code to be rather quick in doing the check in the initialization of
the program.  Would finding the src to CRC or sum and adding that into the
program be the best solution?

Has anyone else dealt with this?



-- 
Christopher Klaus
klaus@mail.lds.loral.com cklaus@hotsun.nersc.gov