Private Kit

On the white paper raskar2020apps.

As mention in the white paper, such attempt on making a location tracking techonology is tricky, because of the socio-techonical aspect. The whitepaper discusses two sides. One side provides information about how contact tracing is important and illustrating the current dillenmma on location tracking and it’s concerns on surveillance. The other side is an advertisement of their proposal PrivateKit, which it’s purpose is to overcome the aforementioned dillemma.

I totally agree on the paper’s premisis and the context the white paper address is already a true contribution to start this discussion. On top of that, listening to the Kevin Salvin really enphasizing that contact tracing is one of the most important things technology can help, when we are dealing with life losts around the world. But It should have not mixed the other side.


This is not discussed throughly, the article repeadly mentions redacting location trace data. If contact tracing is done on top of redacting, this depends on the level of it, and if it’s done before, there is no point of redaction. The white paper is not the place to write the technical implementation of redaction, but it should clearly communicate what accuracy means.

Method and Entity mix

The white paper mixes up methods and entites of contact tracing. Broadcasting could be done by any entity (including individuals, one can easily share their result in twitter), but the paper specifically points broadcasting by a central actor that represents a geolocational region. This excludes corporate entities that also has a strong, if not the dominant actor in surveillance related to technologies. Specifically these coporations are platform providers Apple and Google, and for the Android platform the phones manufacturer. Any attempt using smartphone apps directly interfaces with the operating system of these phones. Fortunately Private Kit is opensource and auditable, we can observe which software libraries and APIs are used for realising this proposal. As the time of this writing, it uses a library that uses an API that it is not clear about user privacy.

The paper should be more clear on separating entites and methods. Or note that Private Kit is only concerned about governmental survailance.

For example, if a government decides to adopt Private Kit, but instead of using it directly it forks it and configures it so that it meets local norm, still opensource. This is fine, and is not broadcasting, but executed and run by the government. I see Taiwan, and Code for XXX efforts as a great meeting point on auditable safe code, but also having governmental support.

Concent of businesses

What does “Depends on government practice” mean? Is it the government requireing the app to get consent to the local businesses? or the government asking for the consent?

The whitepaper indicates that gaining consent is difficult, and yet to overcome the challenges. Private Kit should be clarify on what kind of consent it is asking

Incentives for diagnosed carriers to continue using the app

there will be demand for people that have not yet diagnosed positive, but very little for the ones to continue using it once the user knows he has been infected. The user can simply delete the app or stop using or

On the google doc.

Since the whitepaper only breifly touches the later stages of the app, it is not fair to say anything defenitive about this proposal or link the differences between the initial phase and what is written. It is not clear that which phase will suit for this proposal.

2(a) is effectively boardcasting

The whitepaper draws clear distinction between broadcasting and PrivateKit. Isn’t this effectively

isn’t it possible to request every geohash with every interval?

since we know the trends from 2(a), isn’t the space smaller? there seems to be no limitation how much you can send requests to the server, it’s still possible to send requests in a brutal force way.

central server denial of service or arbitrary data loss


[raskar2020apps] Raskar, Schunemann, Barbar, Vilcans, Gray, Vepakomma, Kapa, Nuzzo, Gupta, Berke & others, Apps gone rogue: Maintaining personal privacy in an epidemic, arXiv preprint arXiv:2003.08567, (2020).