I won't go into the same details as every one else. The only thing I'll say is you're probably going to get your time wasted with this interview process. Initial encryption coding challenge before speaking with a human, a lengthly take home challenge (I spent 20 hours on mine), then an interview to add MORE features to it live, then a "culture" interview, only to be told that they want someone more senior (after passing all technical screenings). Interview process is not difficult, just designed to completely waste your time.