Add a checksum hash to your images for verification (sign your software)

[TNTBOMBOM]

Description of requested feature:

I don't want to rely on GitHub or any website to trust that the software images are authentic and from the developer. Therefore, I need to check and verify their authenticity.

Reasons for adding feature:

https://www.kicksecure.com/wiki/Verifying_Software_Signatures

https://www.qubes-os.org/security/verifying-signatures/

Extra information, such as Shutter version, operating system and ideas for how to implement:

The instructions on how to sign your software are scattered all over the internet.

#594 related.