Comment by ignasl

Probably Berlin. Vilnius or Tallinn could be interesting choices because of friendly business climate, lower taxes, competent and cheap talent, not far away, good tech culture and basically 0% chance that someone would try to outlaw your business (Germany probably has a bit higher chance but I guess it's also not that high). I think US do have some restrictions about exporting encryption to some (all?) foreign countries so you better look closer into that before making a decision. P.S. Stockholm also could be a good place. It's just quite expensive.