While learning from rpm and yum guru Jeff Johnson offlist, the thought occurred that some might enjoy reading

http://www.dwheeler.com/fourfours/

and Dr. Wheeler's thesis entitled "Fully Countering Trusting Trust through Diverse Double-Compiling" at

http://www.dwheeler.com/trusting-trust/dissertation/html/wheeler-trusting-trust-ddc.html.

Enjoy!