[tech] Geminipg: using Gnupg to sign Gemini pages and directories

[nervuri]

On Thu, Feb 25, 2021, Christophe HENRY wrote:
>Nice to meet you :-)

Likewise.

>> Why not use a single SHA256SUMS file for all files on the capsule?  We
>
>Depending on the number of pages, it would become a huge file to
>locally update if one file happens to be modified.

It would be about 1 MB per 10,000 files and it would be updated
selectively by the script.  I think that's generally good enough.
"Premature optimization is the root of all evil." :)

>Indeed, if it was only for me, I would sign the files inline
>(--clear-sign). Or even would add dedicated headers? But, wait, it's
>been discussed ;-)

Inline signatures would work well in some cases.  They are ugly, but
they're otherwise the perfect solution: no extra network requests, clear
indication of which file is signed...

>> I also want to explore the idea of a signed "key-sources" file
>> containing links to the public key from multiple sources, for
>> cross-checking in case the key changes.  Not sure how this would work
>> exactly, I need to give it more thought.
>
>Yes, I totally agree. The good news is that it's already part of the
>Gnupg ecosystem.

You mean keyservers?  They weren't doing so well, last I checked:
https://gist.github.com/rjhansen/67ab921ffb4084c865b3618d6955275f

But it looks like keys.openpgp.org has remedied those issues:
https://keys.openpgp.org/about/news#2019-06-12-launch

Still, it's only a single source.  Are there any other such modern
keyservers?

>> Instead of GPG, I recommend OpenBSD's signify [1], which gives us nice
>> and short Ed25519 keys and signatures.  It's also available on
>> GNU/Linux (in Debian, `apt install signify-openbsd`).
>> (?)
>
>This way, we would lose the web of trust. Wouldn't we?

We would lose the PGP version of it, although there's nothing stopping
you from signing someone else's signify key, to show that you trust it
(and send that person your signature, to publish on his/her site).  This
gives us an ad-hoc web of trust.

I never had the chance to use the PGP web of trust.  It sounds good in
theory, but in practice the UI seriously hinders its adoption.  It might
work within projects like Debian, but if I want to verify a file on the
net made by someone I don't know (and whose PGP-friends I don't know),
the only way for me to check if I have the right key is to get it from
multiple sources and/or network perspectives.  This is what I've always
done, the web of trust never entered the picture.

>> I don't think multiple signatures are worth the added complexity.  But
>> I'm curious if you have arguments to the contrary.
>
>It's a major piece of my thoughts. It's why I would like to keep
>signatures on one file (or even in a header?). Say one famous person
>publishes something great and signed it. On his capsule, there would be
>"page.gmi" and "page.gmi.sig". If I want to keep this by my side or
>want to reuse the page, I can also re-publish the two files.

Ah, ok.  In this case, I would explain in a separate page: "this is the
author's text and this is his signature" (links to both).  Again, an
ad-hoc solution for a rare use case, no technical burden.  This would be
my preference, at least.