[hunter2_]

This could work if the analytics engine is free and (ported to) JavaScript, but not if it's closed source. In the latter case, a trusted third party (escrow, one might call it) as OP described does seem like the way to go.

The problem is, why would end users trust the third party more than the analytics developer? Are there companies that specialize in being this third party and have amassed mutual trust of the general public (akin to a notary public) for handling data and code without leaking either?

[michealr]

Analytics wise, I'm ok with being restricted, other commenters have mentioned looking at WASM as a possible workaround. So local does seem to make the most sense, practicality wise

A thought, the possible scope of services in the data notary or data escrow side of things does seem like an underexplored product category.

[meowface]

Any such data notary/escrow company has a pretty good shot of eventually getting breached (they'd naturally be a prime target, since the attackers could get tons of data from tons of people on behalf of tons of different companies), and that'll possibly destroy that company and maybe also your app. There's also the risk they may eventually have rogue employees, etc.

[hunter2_]

Regular notaries could be as crooked as rogue employees, yet we still use them because imperfect barriers are still barriers (as with security).

But yeah, when computer-related vulnerabilities are thrown into the mix, it could get ugly.

[meowface]

Sure, there's often going to be some centralized source one needs to trust. The issue with a digital escrow vendor is kind of like the issue with cryptocurrency exchanges - one single breach and you immediately walk out with an unfathomably huge treasure trove.

A rogue notary employee can do some damage and notarize things in exchange for bribes, and a rogue bank employee could help siphon some money away, but a rogue digital escrow employee could be bribed to hand over terabytes of extremely sensitive data on lots of big customers, and a rogue cryptocurrency exchange employee could possibly help someone steal hundreds of millions of dollars pretty easily. It's a huge house of cards.

[nindalf]

It doesn't need to be in JavaScript. Any language that can compile to WebAssembly would work too. But I agree with the broader point - the code needs to execute on the client, not the server.