Published on in Vol 7 , No 3 (2019) :March
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/11642, first published
.

1 Privacy and Security (PriSec), Department of Mathematics and Computer Science, Karlstad University, Karlstad, SE
2 School of Informatics, University of Skövde, Skövde, SE
*all authors contributed equally