I've been down this road so many times and I always end up at the same conclusion. When you consider security, privacy, usability, and portability of each authe

I've been down this road so many times and I always end up at the same conclusion. When you consider security, privacy, usability, and portability of each authentication system there are only two that are really viable. SSH keys OR Email/Password. Both of which have their flaws but have proven time and time again to be better than any of the alternatives that have been introduced over the years.