The signing key ID used for source code and RPM releases of BDR versions based on PostgreSQL 9.4 is the key 0x6E192B0E.
To download the BDR 9.4 RPM repository key to your computer:
curl -s http://packages.2ndquadrant.com/postgresql-bdr94-2ndquadrant/RPM-GPG-KEY-2NDQ-BDR-94 | gpg --import gpg --fingerprint 0x6E192B0E
then verify that the fingerprint is the expected value:
9793 74C1 0580 940E 9611 1BE3 A879 B734 6E19 2B0E
The BDR / 9.4 RPM releases key is in turn signed by the 2ndQuadrant master packaging/releases key with key ID 0x2B11E054. You can verify the fingerprint of the master packaging key on the 2ndQuadrant website.
For checking tarballs, download the BDR release signing key as shown above, then use gpg directly to verify, e.g.:
gpg --verify bdr-0.8.0.tar.gz.asc
To check a repository RPM, use rpmkeys to load the master packaging signing key into the RPM database then use rpm -K, e.g.:
sudo rpmkeys --import http://packages.2ndquadrant.com/2NDQUADRANT-PACKAGING-MASTER-KEY.asc rpm -K postgresql-bdr94-2ndquadrant-redhat-1.0-2.noarch.rpm
If you want to manually verify individual RPMs you will need to load the repository key. This is usually installed for you when you install the repository RPM, then yum checks the package signatures after download. So it is not typically necessary to manually verify signatures so long as you verified the repository RPM.
sudo rpmkeys --import http://packages.2ndquadrant.com/postgresql-bdr94-2ndquadrant/RPM-GPG-KEY-2NDQ-BDR-94 rpm -K some-bdr-rpm.rpm
The packaging master key also signs the repository key for the Debian and Ubuntu packages. The current repository key ID for the apt repository is 0xAA7A6805 and can be downloaded from the repository site.