[tech] Integrity checks for Gemini pages

[nothien at uber.space]

nervuri <nervuri@disroot.org> wrote:
> On Wed, 2021-05-19, ew.gemini wrote:
> >Integrity in the sense of "the file remained unchanged in
> >transit"? TLS should take care of that.
> 
> Not necessarily.  The connection can be dropped before the transfer
> completes, or bits in the file can be flipped for various reasons.
> I think there is a place for simple, automated integrity checks - not
> just in Gemini, but also on the Web (like SRI [1], but applicable to all
> links).

Sorry, but that's just wrong.  TLS already provides the mandatory
close_notify signal (and there have been discussions about it before on
this ML) for indicating that the complete text has been transferred.
And every single authenticated encryption method provided with TLS
ensures that the communicated data is the same at both ends - bit flips
and the like are detected and such malformed packets are dropped
appropriately.  One of the mechanisms for this verification is Poly1305
- check it out if you're interested in how and why these work.

> We could, as tidux suggests, use magnet (or IPFS) links for large
> files instead, as those protocols have integrity checking built-in.
> However, this must be weighed against the added friction, both for
> server admins who must install and configure additional software and
> for visitors who don't have a BitTorrent or IPFS client installed.

This is the correct solution.  Note that even protocols like HTTP(S) are
fine (as they - in their effort to support everything - support large
file transfers), so there would be little to no friction.

~aravk | ~nothien