> Published keys are 16 bytes, one for each day. If moderate numbers of smartphone users are infected in any given week, that's 100s of MBs for all phones to DL.
Seems like a usecase for bloom filters or k-anonymity.
16 byte keys for a quarter million people are only 4mb per day.
We aren’t seeing remotely close to a quarter million infections per day. The data sizes are reasonable, even if you multiply it times n days for the backward tracing.
I think his post is a little bit more fearmongering than is necessary.
> I think his post is a little bit more fearmongering than is necessary.
I think that is being unnecessarily charitable because of his high status. His math and his assumptions on this point are completely broken. So broken that if he were some rando, no one would have even read the rest of his thread, much less commented on it at on the front page of hacker news.
This calculation doesn't make sense to me. Since the start of the pandemic, there's been 1.6m confirmed cases so far worldwide. Even if every single one of those were to send 16 bytes identifier, that would still only be 27MB, no?
Where are they getting 100s of MBs per week? I know it's exponential growth and the number of cases will grow, but their calculation still seems off to me.
EDIT: I guess each person has 14 keys, so that makes it an order of magnitude bigger.
His argument is self-defeating. If you have rapid exponential growth and would have to publish hundreds of megabytes of keys per day, this approach of contact tracing is useless and you must instead get the entire population under lockdown. If everybody is sheltering at home, nobody needs notifications of possible contacts, because everybody is doing what would be the response to such a notification already.
This approach, just like the manual approach of tracking potential contacts via paper and phone, is only of use in a scenario with a very limited number of transmissions and an R (reproduction rate) of around or below 1. Its purpose is not to reach such a situation, but to aid in keeping that situation in effect without severe measures. But severe lockdowns must first suppress the infection counts to such levels before any contact tracing may work at all.
We aren’t seeing remotely close to a quarter million infections per day. The data sizes are reasonable, even if you multiply it times n days for the backward tracing.
I think his post is a little bit more fearmongering than is necessary.