[gruez]

The "device ID" part is probably false and a red herring. What actually matters is that google can correlate which challenges a given device is solving, so if it's solving 10k challenges per day, it can be marked as being suspicious.

[repelsteeltje]

Sounds pretty much like they're identify the device, then. Or is "device id" Apple lingo for a specific tech?

[gruez]

No, on both android and ios device id implies some sort of identifier that's reusable across apps. Otherwise a uuid that you generate and write to storage could qualify as a "device id".

[repelsteeltje]

So, essentially a super cookie? That is, generated once (at random or arbitrarily) and then included with proof of work? But not a fingerprint or otherwise linked to identity?

But then that would not work against correlating fraud detection as sketched above. A client could simply reset the app every now and then to generate a new UUID.

[gruez]

>So, essentially a super cookie? That is, generated once (at random or arbitrarily) and then included with proof of work?

You're just describing a regular cookie.

>But not a fingerprint or otherwise linked to identity?

You'll have to reverse-engineer the app to figure out whether it's actually fingerprinting, and whether it's fingerprinting to make sure it's a real device (vs emulator) or it's fingerprinting to uniquely identify someone. I suspect they're complying with app store guidelines and not doing the latter, because it's not worth the PR hit to just to vaguely improve a product responsible for <1% of their revenue.

>But then that would not work against correlating fraud detection as sketched above. A client could simply reset the app every now and then to generate a new UUID.

The attestation result contains a count of attested keys generated in the past 30 days, which detects this case without a "supercookie" that persists across uninstalls.

https://developer.apple.com/documentation/devicecheck/assess...

[repelsteeltje]

> You're just describing a regular cookie.

Yes regular cookie from Google's perspective, but super in that it works across sites. If for some reason you don't just take Google's word you might suspect they collude and share / sell your identity to the site as well...

> The attestation result contains a count of attested keys generated in the past 30 days, which detects this case without a "supercookie" that persists across uninstalls.

Ah. So there is something special limiting control over the UUID? Or is there some way of correlating the physical device to the attestation history?

Why wouldn't I be able to reset and re-enroll in the app and then have it generate me a fresh new cookie attestation history?

[gruez]

>Yes regular cookie from Google's perspective, but super in that it works across sites. If for some reason you don't just take Google's word you might suspect they collude and share / sell your identity to the site as well...

That's just third party cookies.

>Why wouldn't I be able to reset and re-enroll in the app and then have it generate me a fresh new cookie attestation history?

You can get a new uuid, but then that'll be associated with a key that has a high attestation count, which is also suspicious. It's like detecting spam from an account that has 1000 posts in 1 hr vs an ip that created 1000 accounts in one hr making one post each. Both are suspicious.