31–40 of 113 posts
An important question here is: will this framework go away once the pandemic is over? Something tells me it won't.
An important question here is: will this framework go away once the pandemic is over? Something tells me it won't.
So long as all data remains on the physical device at all times and any access or export is _always_ actively initiated by the user, I don't see how it makes the current situation any worse. An abusive government can already subpoena or otherwise monitor all the network providers.
The system doesn't need to ship every key to every phone, much more compact structures like Bloom filters could be used instead. If we assume about 1000 positives per day and each positive uploading 14 days of keys at 4 keys per hour that's a bit over 1 million keys per day. A Bloom filter with a false positive rate of 1/1000 could store that in about a megabyte. Phone downloads the filter each day and checks its obs…
Nothing prevents the user from pushing the checking to some trusted service as well, if they so choose. If they trust the service then they'd upload their seen keys to a checking service, rather than downloading the whole set of diagnosis keys. The important part is the decision is in their hands.
Seems like a usecase for bloom filters or k-anonymity.
Regardless of the technical issues with this, I think the "prank" issue Moxie brings up is much more serious. We've already seen the phenomenon of "Zoom bombing", I can imagine "tracer bombing" would be a much more serious issue. The only way I could see this working is that if when you enter a positive result you have to enter some sort of secret key from the testing authority, but that's totally not tenable given a…
This also seems to address Moxie's concern about public location data being necessary (unless I've missed something). If I only pull all the positive tests from my local county or state, that should hopefully be a small enough dataset to be manageable even on fairly resource constrained low end devices.
The system doesn't need to ship every key to every phone, much more compact structures like Bloom filters could be used instead. If we assume about 1000 positives per day and each positive uploading 14 days of keys at 4 keys per hour that's a bit over 1 million keys per day. A Bloom filter with a false positive rate of 1/1000 could store that in about a megabyte. Phone downloads the filter each day and checks its obs…
> only needs to download the actual keys if there's a potential match.
One of the design constraints of the service was that it should not know your (suspected) infection status unless you give consent that it should be shared.
> Matches must stay local to the device and not be revealed to the Diagnosis Server.
https://covid19-static.cdn-apple.com/applications/covid19/cu...
The better the bloom filter is, the more likely it is that you have actually been in contact with a key if the bloom filter is positive.
Furthermore, the bloom filter has to deal with a lot more keys. In fact, in your example of 1000 positives per day uploading 14 days of keys you only need to upload 14 keys as they only rotate once per day. At 16 bytes per key (as the link above specifies), you'd have to download 14 * 1000 * 16 = 224kb, much less than the bloom filter needs. And this scheme can tell you with 100% certainty whether there has been a match or not, so at least in your example it's much better than bloom filters.
The scalability issues that exist only manifest themselves at larger numbers than 1000 infections per day, say upper tens to lower hundreds of thousands where it starts becoming a problem.
So yes, rough location as moxie suggests is the best method to improve the scheme. Instead of checking the IDs of people thousands or hundreds of km away from you, you could just check the IDs of people in your US state or county. But it has to be smart enough to recognize movement, as in, you need to upload/download all areas you've been in and people living at the borders automatically stand out because they download two or three areas.
Regardless of the technical issues with this, I think the "prank" issue Moxie brings up is much more serious. We've already seen the phenomenon of "Zoom bombing", I can imagine "tracer bombing" would be a much more serious issue. The only way I could see this working is that if when you enter a positive result you have to enter some sort of secret key from the testing authority, but that's totally not tenable given a…
Don't these providers need to be registered somewhere? It should be easy to reach them and provide with either code generator software or even printed one-time codes for database addition.
This is also important because it keeps the framework usable under a variety of adverse and unusual circumstances. An aid organization operating in a disaster zone or impoverished area could make use of such a framework without needing permission from a higher authority or even reliable internet access to the outside world.
Earlier quoted context omitted.
We’re testing like 140k per day with over 2.5M tests total. Obviously more would be better but that’s hardly “almost no testing ability.”
I think it may differ by region. I can say factually that the testing in Texas is absolutely abysmal. Many people who have lots of symptoms are being turned away for testing. On Tuesday our illustrious governor announced with lots of fanfare that Walgreen's would be expanding drive-thru testing using Abbott's 15-minute testing devices. It's now Friday evening and still no word on even where the locations will be for…
Also, how does it compare to DP-3T? (https://github.com/DP-3T/documents) (https://ncase.me/contact-tracing/)
Edit: Apple's preliminary specification was linked in another HN comment. (https://covid19-static.cdn-apple.com/applications/covid19/cu...)