After reading a similar article on HN a year ago, I too decided to use Authy but the realized that it was vulnerable to the same methods. I eventually decided to use andOTP[1].

While it doesn't automatically sync across devices, it does allow you to create backups[2] which can be encrypted with AES or your PGP key. Just store this in Dropbox/Drive/Box and offline storage and you're good to go.

[1] https://github.com/andOTP/andOTP/blob/master/README.md [2] https://raw.githubusercontent.com/flocke/andOTP/master/asset...