Emacs: Failed to verify signature archive-contents.sig

Today i got the message

Failed to verify signature archive-contents.sig

from my Emacs after typing package-list-packages. The full error is listed below:

Failed to verify signature archive-contents.sig:
No public key for 645357D2883A0966 created at 2024-04-22T11:05:03+0200 using EDDSA
Command output:
gpg: Signature made Mon Apr 22 11:05:03 2024 CEST
gpg:                using EDDSA key 0327BE68D64D9A1A66859F15645357D2883A0966
gpg: Can't check signature: No public key

It seem’s that i wasn’t able to install elpa-packages anymore.

After some research i got the hint to install gnu-elpa-keyring-update with the Emacs-package-manager to solve this problem.

That sounds easy but before installing a package i had to temporary set the following variable to disable the keyring-check:

(setq package-check-signature nil)

After that i call package-list-packages again an installed gnu-elpa-keyring-update.

To be on the safe side, i restarted Emacs and the error was gone.