[LINK] Schneier on COVID-19 Contact Tracing Apps

[David Boxall]

Schneier stating the obvious:

==============================================================================

I wasquoted 
<https://www.buzzfeednews.com/article/carolinehaskins1/coronavirus-contact-tracing-google-apple>in 
BuzzFeed:

    "My problem with contact tracing apps is that they have absolutely
    no value," Bruce Schneier, a privacy expert and fellow at the
    Berkman Klein Center for Internet & Society at Harvard University,
    told BuzzFeed News. "I'm not even talking about the privacy
    concerns, I mean the efficacy. Does anybody think this will do
    something useful? ... This is just something governments want to do
    for the hell of it. To me, it's just techies doing techie things
    because they don't know what else to do."

I haven't blogged about this because I thought it was obvious. But from 
the tweets and emails I have received, it seems not.

This is a classic identification problem, and efficacy depends on two 
things: false positives and false negatives.

  * False positives: Any app will have a precise definition of a
    contact: let's say it's less than six feet for more than ten
    minutes. The false positive rate is the percentage of contacts that
    don't result in transmissions. This will be because of several
    reasons. One, the app's location and proximity systems -- based on
    GPS and Bluetooth -- just aren't accurate enough to capture every
    contact. Two, the app won't be aware of any extenuating
    circumstances, like walls or partitions. And three, not every
    contact results in transmission; the disease has some transmission
    rate that's less than 100% (and I don't know what that is).
  * False negatives: This is the rate the app fails to register a
    contact when an infection occurs. This also will be because of
    several reasons. One, errors in the app's location and proximity
    systems. Two, transmissions that occur from people who don't have
    the app (even Singapore didn't get above a 20% adoption rate for the
    app). And three, not every transmission is a result of that
    precisely defined contact -- the virus sometimes travels further.

Assume you take the app out grocery shopping with you and it 
subsequently alerts you of a contact. What should you do? It's not 
accurate enough for you to quarantine yourself for two weeks. And 
without ubiquitous, cheap, fast, and accurate testing, you can't confirm 
the app's diagnosis. So the alert is useless.

Similarly, assume you take the app out grocery shopping and it doesn't 
alert you of any contact. Are you in the clear? No, you're not. You 
actually have no idea if you've been infected.

The end result is an app that doesn't work. People will post their bad 
experiences on social media, and people will read those posts and 
realize that the app is not to be trusted. That loss of trust is even 
worse than having no app at all.

It has nothing to do with privacy concerns. The idea that contact 
tracing can be done with an app, and not human health professionals, is 
just plain dumb.

https://www.schneier.com/blog/archives/2020/05/me_on_covad-19_.html

-- 
David Boxall                    |  Any given program,
                                 |  when running correctly,
http://david.boxall.id.au       |  is obsolete.
                                 |       --Arthur C. Clarke