OK, last time I was trying to install package with rpm command and I get "missing GPG db42a60e key" error message.
rpm command try to verify the integrity of downloaded software/package program. You may also see this error message with up2date command.
To fix this problem just download missing GPG key from RedHat's web site (or use your distributions web site i.e. CentOS/Fedora Core site):
# wget http://www.redhat.com/security/db42a60e.txt
Now import missing GPG key from text file - db42a60e.txt:
# rpm --import db42a60e.txt
Now you have imported the GPG key to verify the packages and this error message will go:
# rpm -ivh foo.rpm