Package: debian-cd There is no gpg signature for SHA256SUM file. So there is no way to verify the images originates from the debian.
Via http:// do: debian.org -> Getting Debian -> Download an installation image -> Tiny CDs, flexible USB sticks, etc. -> amd64 -> http://ftp.nl.debian.org/debian/dists/stretch/main/installer-amd64/current/images/
pgpr0EkldT5Qx.pgp
Description: OpenPGP digital signature
