AWS's public certificates for the base64-encoded instance identity
signature (IMDS `/latest/dynamic/instance-identity/signature`), one per
region, from
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/regions-certs.html
(the RSA certificate (the one for the base64-encoded signature; not DSA, not RSA-2048)). A region with no file here has no
certificate, and a box there never verifies. Add a region's file before
running a second box in it.