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Why SARS-CoV-2 Bluetooth contact tracing apps are a tremendously stupid idea (raccoon.onyxbits.de)
27 points by bluegopher 2240 days ago
11 comments

> Bluetooth contact tracing is hyped as a silver bullet, an alternative to social distancing.

What a ridiculous straw man argument. Nobody is saying this is a silver bullet. Nobody is saying it replaces social distancing. That's either disingenuous or it's based on a massive misunderstanding of the purpose here.

It is one weapon in an arsenal of several, and the goal is to keep using all of them at once because each one helps reduce R0. Contact tracing doesn't replace everything else. You keep doing as much social distancing as you can. You keep washing your hands. And you also do contact tracing.

> Day 6 [ ... ] Joe’s test results are back: positive. [ ... ] Potentially a few hundred people are going to have a really rotten day.

Yeah, well, that is the idea, isn't it? They were possibly exposed. Sometimes learning bad news means you have a bad day. What's the alternative, ignorance is bliss? You might also have a bad day if you get COVID-19 and give it to your grandmother and then she and half the people in her retirement home die.

Thank you. the "anti tracing app" crowd seems to be split into two teams, one "Gov are going to use this to abuse and control you" or "it wont stop you getting the virus, it wont protect you from getting it"

this is NEVER the plan. why cant people get over that fact? Like home made masks, they're a small layer that helps to reduce the rapid spread. slow it down, let us control it a bit more.

"Ask a computer scientist for their opinion and the answer is: FUCK NO!"

Of course, because all computer scientists share the same opinion... not!

Some computer scientists are even aware of the limits of their knowledge and understanding and give answers like "it depends". There are tons of variables that play into how well any of these solutions work, and yes, there's a privacy trade-off. Just like with license plates, card payments, mobile phones and leaving your house. Or using Linux. Are you one of the 10 people using Linux on the Internet? Yeah, we know who you are ;-) Welcome to the real world, where people make compromises.

Also: do you really want to be the guy saying something doesn't work while others are currently trying to make it work?

You mean like really tamper proof electronic voting(in practice, under real world constraints of yadda yarr yarr yadda)?
The comment above lists many solutions that require compromises to work.

We can make compromises on a covid-tracking app. Worst case scenario: fewer people install it and it's less effective—still better than not having it in the first place.

We can't make compromises on a voting system—worst case scenario: democracy is overthrown forever.

There is a BIG difference in the threat models here. The prople objecting to electronic voting recognize that a major breakthrough in computing security is needed before we get there. OTOH we van probably design a _reasonable_ covid app with acceptable compromises.

If you think that having your position tracker is unacceptable: great for you, stand up for your rights. Most people do have google maps and its tracking installed, and don't give a crap _because it lets them see traffic_. I think the tradeoff here is definitely better.

Obviously there will be false positives and false negatives with this app. If you could catch even 50% of cases though it would go a long ways towards stopping spread. The question is whether you can get that without a huge false positive rate. My guess is that you can, since it appears that the primary transmission mechanism is sustained indoor contact, within about 15 feet. You could probably increase the accuracy if you could detect being indoors.

On the cost issue, the obvious solution is to make testing free and easy, and to provide a financial incentive to get tested quickly after the app alerts them.

> The question is whether you can get that without a huge false positive rate. My guess is that you can

No, you can't. The virus spreads exponentially and the app is suppose to keep up. In other words, you get an exponential number of alarms.

> On the cost issue, the obvious solution is to make testing free and easy

Cost is not the limiting factor. Equipment, reagents and time is. We could have easily beaten the pandemic by now if simply going from door to door and taking a smear test was an option.

the whole point of the app is to isolate people that have been in contact with positive cases before they become contagious.

if everyone has the app, you won't have an exponential growth.

https://www.youtube.com/watch?v=gxAaO2rsdIs

I think the author might be under the false impression that coming in contact with a known positive has some repercussions for you. In reality, it's just an indication that you should get tested.
> government agencies and law enforcement … to be honest, I have no idea why they should be interested, but surely, they will.

This one’s easy. Bob commits a crime. Police think there’s an accomplice. So, they use a contract tracing system to identify and start investigating Bob’s direct and second-order “contacts”.

Note - this is independent of the actual implementation, which does seem fairly secure against such uses. Still, I worry that given the public nature of the “infected” list, and that phones automatically add themselves to the list, there are some statistic correlations which could be made.

> So, they use a contract tracing system to identify and start investigating Bob’s direct and second-order “contacts”.

If "identify" means to discover the identity of, I don't see how law enforcement can do that under the Google/Apple system.

Law enforcement can get Bob's phone. And it will have a list of all the pseudonymous ids it collected. They can pull that data, but what do they do with it? The ids aren't IMEI or phone number or anything. And there is no central database of them.

If you had the contact's phone, then you could get data off both phones and confirm whether they had been nearby. But if you're confirming a link between Bob's phone and someone else's phone, it means you already discovered the identify of the contact through other means.

It would be possible to build a central database of these ids through dragnet surveillance, but since they are stored locally only, that would require putting malware onto the entire population's phone to upload the ids somewhere.

law enforcement already has location from cell tower data.

to be able to read the ids from contact tracing apps, they need to capture the phones and decrypt them, at which point there's probably more evidence to be found than some random ids

Actually no and no.

Having been in the same cell (potentially several square miles) as the murder victim is not quite the same as having been in tracing distance (4m²).

That's quite a strong argument/pretense, why law enforcement would immediately lobby to get the system changed in their favor. Don't you agree?

if you use an android phone, check this URL: https://www.google.com/maps/timeline

that information is a lot more sensitive and a lot more useful to law enforcement. most people don't even know how much your location is being tracked.

the contact tracing framework by comparison, isn't really very useful for anything other that just that...contact tracing

sure, they can lobby for that....they have been lobbying for backdoors since the 90s.

the way the contact tracing framework ACTUALLY works makes it doesn't really make it useful to them.

they could lobby to change it

they can lobby with or without the framework being implemented

Contact tracing apps sounds like a totalitarian wet dream.
A couple of concepts that I think the OP has wrong. I'm only talking about the Apple-Google contact tracing framework:

* you need a key from a doctor to be able to mark yourself as positive.

* when you get a notification that you came into contact with someone positive, that's it....nothing else happens. it's up to you to go get tested (possibly with a priority because of the app)

* you are giving up 0% privacy by using contact tracing

the author doesn't seem to understand how to system works. yes, it's not perfect, it doesn't tell you you've got it for sure, just to get tested, in case you've been near someone who has it.

Also, people can't troll using the app, you'll need a key to be able to mark yourself as infected

The article is pretty good and the author seems to understand how the app works, can you provide some specifics?

I think giving up a significant amount of privacy for technology that’s “not perfect” is a pretty dangerous slippery slope.

you are giving up 0 privacy. no tech is perfect, but this is very well thought out.

i've gone into detail here: https://news.ycombinator.com/item?id=23053624

The point of the article is discussing why the system can't work as promised ("anonymous", "voluntary") and has to devolve from "decentralized and privacy aware" to "shit in a bun".

Yes, you need a key and the article explains why that's the case and why you don't want one.

where does your article talk about the key?
It will help the legions of people employed to do contact tracing manually right now in places like taiwan korea and singapore..
And "fuck no!" is indeed the right answer.
why?
The reason is explained in the article where the quote comes from.
none of the reasons make sense sorry about the formating, but i've tried to cover all of them:

Joe the hacker What if Joe stayed home the first day (did not get infected), got hold of Jane’s phone and decides to swat her for fun?

// What does that have to do with anything?

Joe, the slacker What if Joe was not a neighbor of Jane, but one of her students, desperate to meet a deadline. Could he buy himself an extension by faking an infection?

// not really sure what this has to do with the tracing app...you can't fake an infection on the app, you have to get tested

Joe, the movie buff What if Joe had invited Suzie to the movies and turned his phone off before entering the cinema hall?

// who the fuck turns off their phone in a movie theatre?

Joe, the deceived Plot twist: Joe just caught the flu. Same symptons, different pathogen. Should he wait for test results (or be tested at all) before hitting the alarm?

// Again, you can only tell your app that you are infected with a key that you get after you test positive.

Joe, the unprepared Joe is single. What if he runs out of food while quarantined? Will he sneak out, leaving his phone at home?

// not sure why he's leaving his phone at home? who does that? even if it does happen, it will be rare.

Joe, the kindergarten teacher What if someone had the idea to reopen kindergarten, thinking the availability of Bluetooth contact tracing renders social distancing unnecessary?

// people want to open kindergartens because 'MERICA...not sure how this app will change things

Jane, the hypochondriac What if Jane had an unrelated symptom, quarantined herself without a test and thinks, she gained immunity afterwards.

// what does this have to do with the contact tracing app?

Jane, the gym instructor How many contacts would Jane’s phone log, if she left it in the locker room?

// I don't think most people leave their phones in the locker room. Even if they do, they will have contacts...other people that are in the gym at the same time.

John, the secret agent Are there countries that would benefit from keeping other countries in lockdown? If so, what could be more effective than interlinking as many people as possible, then sending a fake alarm?

// ugh...sure...I guess...if they're bored? and they get a key from a doctor

101010, the software bug Is it possible that a piece of software, especially one, that is based on a bad idea and coded in a hurry, might malfunction?

// pretty much everything around us runs on software...yes, there might be bugs, they get fixed

If you have bars open then there's no point of doing anything to stop spread.

Just focus on inventing vaccine for couple hours a day then hit the pub.