Add signing to ZIM files to attest the origin of the archive

[mofosyne]

How much would it be to extend the ZIM format to include some form of cryptographic public/private key attestation that the ZIM archive has not been tampered with and has been generated from a trusted source.

This will be very useful for distributing stuff like wikipedia dumps over flash drives in a way that can be verified to be trusted.

[rgaudin]

Couple infos (not responding to your question)

• ZIM files include a checksum already, I believe to prevent accidental alteration to files.
• It's not displayed in Kiwix readers AFAIK
• It's not displayed next to downloads
• There's a zimcheck binary that returns whether the ZIM data matches the in-ZIM checksum.
• zimcheck is not included in Kiwix readers AFAIK.

[mofosyne]

Looks like this is already a known request openzim/libzim#40 on the backend