Going back to the summer of 2016, I had the opportunity to attend a summer school on information security. It was the International School on Foundations of Security Analysis and Design (FOSAD) held in the University Residential Center of Bertinoro, Italy. FOSAD is one of the best Ph.D. summer schools I have ever attended.
There were various outstanding and demanding presentations on a wide range of topics, including mathematical models, analysis tools, and Internet security, as well as formal verification of security protocol implementations, practical system security, and others. We also covered information security from a practical perspective as well.
Aside from education, we also enjoyed the Italian countryside, breathtaking views, exquisite food, and some local wine. I had the opportunity to meet and mingle with exceptional students from all around the world, as well as professors from renowned universities. This also helped me in the expansion of my academic network.
If you are a Ph.D. student or simply you want to delve deeper into the intricate world of information security, I recommend attending FOSAD, preferably in person. It is a challenging summer school, but it is one of the best schools I have ever attended.
Here is a group photo from that event.

More details about FOSAD can be found on their website: https://sites.google.com/uniurb.it/fosad
Finally, if you want to learn more about security-related Ph.D. courses organized in Sweden, I highly recommend that you visit the website: https://swits.hotell.kau.se/Courses/SWITS-PhD-courses-in-IT-security.htm
Also, please feel free to drop me an email or a tweet in case you want to know more about Ph.D. courses in general.