Please note that Germany has (compared to other EU members) quite strict and company-friendly protesting laws.
Such protests may be even considered as political protest (Politischer Streik) which makes them not illegal per se but could be illegal. https://www.bpb.de/themen/medien-journalismus/netzdebatte/219308/ein-bisschen-verboten-politischer-streik/
Here you go:
https://www.bleepingcomputer.com/news/security/this-image-shows-its-own-md5-checksum-and-its-kind-of-a-big-deal/
(MD5 is not PGP, but impressive nonetheless)