Verifying authenticity of Debian CDs

[Semih Ozlem <semihozlemlinuxuser@gmail.com>]

On the web page

https://www.debian.org/CD/verify

I am trying to follow the next paragraph.

"To ensure that the checksums files themselves are correct, use GnuPG to verify them against the accompanying signature files (e.g. SHA512SUMS.sign). The keys used for these signatures are all in the Debian GPG keyring and the best way to check them is to use that keyring to validate via the web of trust."

when I run the command

gpg --verify SHAxSUM.sign SHAxSUM

I get a message saying that

Can't check signature: No public key

How should I proceed to get the necessary public key.

I tried following the link on this page to https://keyring.debian.org/

but I was not able to follow what to do. I tried simple copy and paste of commands on this page, or their small variants, but was not able to get any results.

Can someone help please

Thank you in advance.

Semih Ozlem