[mschwaig]

I think it would have been a good thing to mention, but difficult to do well in more than a quick reference or sidenote and could easily turn into a extensive detour. I'm saying this as someone who's working on exactly that topic. There is a little bit of overlap between the kind of quantitative work that they do and this design aspect: the extensional model leaves the identity of direct dependencies not entirely certain. In practice that means we don't know if they built direct dependencies from source or substituted them from cache.nixos.org, but this exact concern also applies to cache.nixos.org itself.

The intensional store makes the store shareable without also sharing trust relationships ('kind of trustless' in that sense), but only because it moves trust relationships out of the store, not because it gets rid of them. You still need to trust signatures which map an hash of inputs to a hash of the output, just like in the extensional model. You can however get really powerful properties for supply chain security from the intensional store model (and a few extra things). You can read about that in this recent paper of mine: https://dl.acm.org/doi/10.1145/3689944.3696169. I'm still working on this stuff and trying to find ways to get that work funded (see https://groundry.org/).