[0xBeefFed]

It should be noted that your privacy is not preserved if you test positive and need to upload your Daily Tracing Keys to a server. Your broadcast IDs for an entire day can be linked together, making it easier to de-anonymize you. I understand that they use Daily Tracing Keys to reduce the demand of the backend server, but I think it would be better for user privacy if they either reduced the linkable period from a day to say an hour, or used an unlinkable design.

[pintxo]

In case you test positive, and we actually have the resources to trace your contacts, your privacy will be gone in todays system for sure.

As you'll have to provide information about your recent contacts to the authorities performing the contact tracing. At least that's how I understand our local law (Germany).

So I don't think its necessarily worse doing it with an App than doing it the old fashioned way. Sure digital traces are always easier to abuse, but then on the other hand, because things get automated, actually less people might get access to your data. Which would be a privacy win.

I believe what's even more important than how we design the app, is how we design the legal framework around it. We do need rock solid laws, having enforceable data retention periods, and that limit access to the pare minimum needed.

Unfortunately, our track record for the design of such laws has not been too good over the last years.

[TechBro8615]

I can assure you that most people, if they were buying drugs or cheating on their spouse, will omit certain contacts from any “manual” tracing effort.

[Reelin]

I'm not sure if you intended that to be positive (ie tracing might be more complete in some cases) or negative (ie concerns about not wanting to reveal certain data). I'm going to go ahead and respond to the negative interpretation in case any future readers interpret it that way.

This is true, but I think a DP-3T like protocol (ex the Apple-Google spec) doesn't actually pose much risk here. The hypothetical drug dealer or other illicit contact can receive a notification that they were potentially exposed to someone that was infected, but in general no one else (a police officer, a spouse, etc) will be able to determine who was in contact with who.

In order to link someone to a particular location, you would need to observe their broadcast identifier while they were there and also link their diagnosis key back to them (this is likely to be quite difficult for most actors to accomplish).

In order to reveal a contact between two people, you would either need to do the above for both of them or to observe at least one of them at that location and time in some other manner.

[TechBro8615]

I’m sure the protocol is fully privacy preserving, now. But if we give an inch, the government will take a mile. This is about normalizing self-surveillance and isolating ourselves in response to notifications on our phone. Sure, the tech is privacy-preserving now. But who’s to say an emphasis will remain on privacy in future iterations of the technology?

Personally, I will not opt-in to this technology, and if forced to use it, I will leave my phone at home. It’s a small act of civil disobedience but it’s a necessary one IMO.

It’s alarming to me how so many in tech seem welcoming of, even excited for, this technology. I say this as someone who wrote my senior thesis on a subject related to privacy enhancing technology, so I’m familiar with the ideas.

[Reelin]

> It’s alarming to me how so many in tech seem welcoming of, even excited for, this technology.

It gets contact tracing right by accomplishing the goal while yielding almost no ground on privacy and remaining almost entirely offline. In an ideal world, all new technologies would be implemented in such a focused manner without regard for turning a profit.

I'm puzzled by your concern about normalization of self-surveillance; everyone I know has already voluntarily made drastic alterations to their behaviors due to current circumstances. I really don't see what introduction of this technology changes.

> who’s to say an emphasis will remain on privacy in future iterations of the technology?

If people don't object to widespread state surveillance later, would they have objected now? I don't see why a decentralized technology specifically built to prevent surveillance should lead to an increase in acceptance of it.

[0xBeefFed]

The difference is that the old system relied on human memory which is fallible, not to mention you can omit details which would lead to further trouble (infidelities for one). In this system the only control a user has is to turn off bluetooth, or leave their phone at home if Apple/Google override the users ability to turn this off.

[skybrian]

I think it's up to you to upload the data? It seems like it depends how the app is designed. The protocol doesn't specify it.

[0xBeefFed]

The protocol states that it will upload the Diagnosis Keys, a set of Daily Tracing Keys relevant to your exposure. So in short, if this is the case it forces the user to either upload all their keys or none.

I would like to note that a v1.1 has recently been released, my information is about v1.0.

[Reelin]

The specification (at least v1.1) contains nothing about uploading keys. The API appears to provide only the minimum required for protocol implementation.

The ENSelfExposureInfoRequest class can be used by an app to obtain diagnosis keys for the previous 14 days. What an app does with those keys is up to whoever implements it.

https://covid19-static.cdn-apple.com/applications/covid19/cu...

[0xBeefFed]

That does not seem to line up with their cryptography specification, which is where I am getting my information from. Thank you for mentioning this

[gruez]

I thought only the DTKs are uploaded? That is, you can censor your activity on a day-to-day basis but not on an hourly basis.

[closeparen]

Under what circumstances do you think it would be okay for an infected person to hide their contacts? Surely you’re not valuing your marriage over the lives that will be lost in the resulting spread?

[0xBeefFed]

If a user is in close confinement with someone they fear will lash out at them if they test positive, for one. Off the top of my head, lets say you take an Uber home and the driver now has your home address, you don't know if they will try and attack you.

This is an example off the top of my head, as other comments in this thread have explained, violence against people who have the virus is happening around the world and is something that must be accounted for in these protocols.

Edit: a link to a story from another comment (https://www.washingtonpost.com/world/the_americas/coronaviru...). I hope you can see that this technology can worsen this.

[closeparen]

The system doesn’t say who your affected contact is, only that you have one. The driver has no way of knowing it was you.

[0xBeefFed]

If you have a Bluetooth receiver logging the different IDs you've come in proximity with and when, its easy to deduce who the positive user is by who you were in proximity of at that time.

[cm2187]

Well, let's keep in mind it is decentralised, so only people who have been in contact with you can correlate it with your location at a given time in the past. Not the whole world nor a central authority.

And even is someone goes to that extent to track your identity down, I am not sure that local de-anonymisation is a problem. This is not something like HIV. I don't think there is any social stigma to catching the coronavirus. If you catch it you should self-isolate, and it will be obvious to the people around you that you got it. And if you don't want to self-isolate and want to hide it, what is the point to self declare that you got contaminated on the app in the first place?

[jstarfish]

> I don't think there is any social stigma to catching the coronavirus.

"In Mexico, Colombia, India, the Philippines, Australia and other countries, people terrified by the highly infectious virus are lashing out at medical professionals — kicking them off buses, evicting them from apartments, even dousing them with water mixed with chlorine."

https://www.washingtonpost.com/world/the_americas/coronaviru...

...and these are cases where the victims don't even have the virus.

Disease has always carried stigma. We tend to lash out at things we don't understand. History has seen everything from leper colonies to menstruating women herded into tents.

You or I may be able to rationalize it and say "well, shit, the test was positive-- time to self-isolate" but plenty of plebes will use it as cause to incite a witch hunt, especially if a loved one dies from it and transmission is attributable to you.

[cm2187]

OK, that's a fair point, but it would take someone uneducated that believes in the stigma to also be a tech wiz to collect and correlate the data. Presumably the app won't tell you when and where the contact happened (and if so, no implementation of contact tracing is anonymous since the app won't know that you were in a busy bus full of strangers or in a small office with a single colleague).

[jstarfish]

> it would take someone uneducated that believes in the stigma to also be a tech wiz to collect and correlate the data

Not quite. It takes a wiz to collect and correlate the data, yes. What happens to that data after that? For it to be useful, it's going to get stored somewhere. All it takes is an uneducated clerk or bored intern with access to go snooping around the de-anonymized data to compromise anybody implicated.

And this does happen routinely.

* Facebook, Uber and Google have all had problems with plebes (and tech wizzes!) with god-tier access doing inappropriate things with sensitive data.

* Bored data entry clerks with access to the credit reporting database routinely snoop on neighbors', exes' and celebrities' credit reports in spite of federal law.

* Revenge porn is such a thing that rule 34(a) ought to be that if you produce nudes, your confidant or Geek Squad/iRepair technician will post them on the internet.

* Look at how often people get doxxed by employees leaking customer PII onto reddit and 4chan, then look at how fast the mob descends on people innocent of any actual wrongdoing.

* We've seen a secretary get her hands on the Pepsi formula and try to sell it to Coca-Cola.

* The people living in the geographic center of America continue to receive death threats and harassment because of a flaw in outdated MaxMind databases that attributes ungeolocatable IPs to their location.

* There are people who refuse to participate in the census because of what certain cults of personality have done with such data.

Any chain of confidentiality is only as strong as its weakest link. You presume far too much intelligence and rationality on the part of humanity. Never forget that half of Americans wanted a belligerent narcissist to be "leader of the free world," and he still has supporters despite publicly recommending anti-parasitics and Lysol douches as solutions for a global viral pandemic.

Sensitive data is not created and left to decay in an underground bunker in Yuma. Despite its practical uses, at some level it will be exposed to individuals who lack discretion and will be exploited to malevolent ends.

Not once in human history has it worked out any other way!

[azinman2]

The deanonymized data doesn't exist except on your own device.

[Reelin]

It's a bit more complicated than that. What's being suggested here is that it would be possible for a bad actor to observe all Bluetooth activity over a large area. They could then use a diagnosis key to reconstruct someone's path through this monitored area, and then deanonymize that person by combining their path with other data sources. Later, an uneducated and hostile individual might somehow gain access to this deanonymized data and abuse it.

[wtmt]

People who are educated tech wizards can also have the same stigma. There are many factors at play in places that have more diversity and existing problems between communities (like race, religion, class, etc.). Hopefully, like you said, the app won’t tell you when and where the contact happened. But we still need to make sure that we have as much privacy protection as possible while making this useful.

[wtmt]

> I don't think there is any social stigma to catching the coronavirus.

Sadly, this is not true in India. Infected people have been threatened by their neighbors and friends with death. Infected people have also been harmed. Doctors, nurses and healthcare workers who have been caring for COVID-19 patients have been evicted from their houses or physically harmed (the latter forced the government to bring an emergency law providing for stringent punishment for those who attack healthcare workers).

I’m guessing that there will be a social stigma depending on the culture as well as other factors like the mortality rate (if your area has a higher mortality rate, then you’d likely hate infected people and take matters into your own hands).

Humans can very quickly develop irrational fears and react on that.

So there is a huge need to preserve the privacy of those infected.

[0xBeefFed]

So all of the tokens are being put on a central server. Today, governments use WiFi and Bluetooth to track traffic. It is not far fetched to see that your commute from point A to B could be tracked using Bluetooth receivers in transit stations.

This technology is currently being used to track people today. The use of Bluetooth address randomization does not do a sufficient job to prevent this, the only option is to not use Bluetooth.

It is important that people are aware of these risks. I am fortunate to live in a place where I can live my life without scrutiny from the government, but not all are afforded such a luxury.

[cm2187]

Even if they do that, they can only track the people who self report as contaminated for the period during which the self reporting applies (i.e. n days before testing positive). Not before, not after.

But I just can't think of a system that achieves contact tracing while no one having any idea of the whereabouts of a person who self declares as contaminated. At one point the person who self declares has to volunteer to disclose some information.

[0xBeefFed]

I think its important to give the power to the people by allowing them to omit tokens from sensitive time points. In the current protocol, that means losing a whole days worth of contacts. If you reduce the period to an hour, you still allow people to share the contacts made on their commute or their lunch break without divulging or tracing them back to more sensitive time periods they don't want to be traced back to.

[cm2187]

That’s one side of the ethical question, but what about the other side, what about the people who have been in contact during the period where the infected person would rather not have its location disclosed?

And it is a bit theoretical, as the authorities who have the capability to track your blutooth across the city have many other ways to track you (starting by calling your phone service).

What I object here with the NHS is the creation of one more tracking database with the explicit intention to let some researcher roam through it to find something interesting.

[0xBeefFed]

I appreciate you looking at the other side. To explain my view point, in this system it seems like all of the risk is put on the infected party who reports themselves. By decreasing the level of control they have, I believe you will see a decrease in the number of adoptions. It is valid to think about the non-infected user wanting to have this information, but today they don't even have this information so to even know they were exposed on their commute is above and beyond what is in place today.

I guess my original comment is a bit vague. When I look at these protocols I am interested in how large scale adversaries (Nation State) would use this technology, but also small scale adversaries (day-to-day person you are not friendly with). I think its also important to note as others have, that being outed as having the virus does put people at risk of violence in some places.

[TechBro8615]

> I don't think there is any social stigma to catching the coronavirus.

Maybe not. But there is definitely a social stigma about certain activities, like meeting your drug dealer or cheating on your spouse, which would be revealed through automated contact tracing.

[cm2187]

It would only be revealed to your drug dealer or to whoever was in the vicinity.

[candiodari]

And to the authoroties, who then promise to not violate that promise.

Except they refuse to be limited by cryptographic means to that.

Why? Because they demand the ability to change their promise in the future ... exact details to be specified. Perhaps “solving drugs” with contact tracing. At which point they have your data, you have zero control, and “your honour we can prove he lied: he was close to that drug dealer 5 times. Further details (such as that this happened in the train station and 5000 other people were also close) cannot be confirmed because that would violate privacy”.

This is the government that got caught letting police officers stalk their ex for 2+ years and then initially arrested the victim for more than 2 weeks when caught. Let’s not pretend they’re above doing this, especially since it’s become increasingly clear this contact tracing is the police’s wet dream.

[closeparen]

With any luck, we will create stigma a hundred thousand times more powerful against deliberately helping the virus spread.

[tomjen3]

Try to walk through a public place with one of the medical masks (if you can source them). Practically everybody moved as far as they possibly could.

But yeah there has been lots of stories about medical personnel who where thrown out of their rented places because of the fear of the virus.

[azinman2]

This is almost never actually the case. Your daily keys are random, so the only way to know it's you is for someone to monitor bluetooth devices near by, and associate those keys with a physical identity... which becomes very difficult unless there's only one other person you come into contact with. In practice, it provides about the best anonymity you could ask for.

[red0point]

Valid point. DP3T (in one configuration) adresses this and lets you filter out certain parts that you do not wish to disclose. Thus, this then requires you to upload all broadcast identities used in the relevant timeframe, but because of space-related issues is then „compressed“ using a Cuckoo-Filter. This, however, yields false-positives. To eliminate those to a managable amount, it further requires more space.

So, this has a tradeoff. Personally I don‘t think that linking multiple IDs in a day is a big intrusion of your privacy (and remember, it‘s only disclosed to anyone for the timeframe that is epidemologically relevant) - full de-anonymization still requires some second channel, such as cameras or the like - which can be linked together without those Broadcast IDs anyways.

[radicalbyte]

The thing with Bloom/Cuckoo filters is that you can play around with the parameters and, for example, provide a set of filters for a day in such a way that the app users can do a binary search.

It never provides a false negative so all positives can download their set-up filters until they're satisfied.

The filter that DP3T are describing isn't that much bigger than the DTK set anyway.

[0xBeefFed]

The unlinked DP-3T is one extreme, there is a happy medium if developers don't want to use Cuckoo Filters or Bloom Filters due to false positives, which is to decrease the linkable period. If the period was an hour, people could freely share legitimate tokens for their commute, but hide the ones where they had an hour long 1-1 with their manager.

[user5994461]

It's hard to test positive given the extremely limited supply of tests and all the effort you'd have to go through to get tested. I really can't imagine anybody willingly testing -more so with new invasive tracking- unless they are really ill and in need of medical attention.

[0xBeefFed]

The issue is, if your putting the risk on infected users, what is the benefit to them to release their tokens? They are already at risk, this just makes them bigger targets.

[marblar]

The recorded broadcast IDs can be linked together, but only if they are somehow gathered from all of the devices that have been near you. As far as I can tell, the spec doesn't include recorded broadcast IDs ever leaving the device.

[xfitm3]

If I keep my phone in a RF blocking bag and remove it only when needed I will have some semblance of privacy. I don't care about push notifications.