  For the protection of people and society against harm and health threats --
especially for the COVID-19 pandemic -- a variety of different disciplines
needs to be involved. The data collection of very basic and health-related data
of individuals in today's highly mobile society does help to plan, protect, and
identify next steps health authorities and governments can, shall, or need to
plan for or even implement. Thus, every individual, every human, and every
inhabitant of the world is the key player -- very different to many past
crises'. And since the individual is involved -- all individuals -- his/her (a)
health and (b) privacy shall be considered in a very carefully crafted balance,
not overruling one aspect with another one or even prioritizing certain
aspects. Privacy remains the key. Thus, the solution of the current pandemic's
data collection can be based on a fully privacy-preserving application, which
can be used by individuals on their mobile devices, such as smartphones, while
maintaining at the same time their privacy. Additionally, respective data
collected in such a fully distributed setting does help to confine the pandemic
and can be achieved in a democratic and very open, but still and especially
privacy-protecting world. Therefore, the WeTrace approach and application as
described in this paper utilizes the Bluetooth Low Energy (BTE) communication
channel, many modern mobile devices offer, where asymmetric cryptography is
being applied to allows for the decyphering of a message for that destination
it had been intended for. Since literally every other potential participant
only listens to random data, even a brute force attack will not succeed.
WeTrace and its Open Source implementation is the only known approach so far,
which ensures that any receiver of a message knows that this is for him/her,
but does not know who the original sender was.
