Secure and verified way to get the Postgresql RPM's

LS,

My company has the policy only to use secure verified software from the
Internet. Therefore I've two questions for you:

1) Is the a secure way to get the GPG key for the postgresql software?
Currently this is only down-loadable from your public website without a
way to verify this is indeed the one and only postgresql source.

2) Can you guarantee that software from your unsigned website is indeed
the one and only software you provide?

Kind regards, Luitzen van Gorkum