gpg error on apt-get update

[Richard R (Dick) Rutledge]

Would somebody be able to direct me to where I could find the public 
keys for
http.us.debian.org and non-us.debian.org.  When running "apt-get update" 
I am told the public keys are not available and that I should run 
"apt-get update" to fix the problem.
I have gone round and round trying to figure this out and would 
appreciate and help.

Thank you
Dick Rutledge