Nitrokey is described as 'Email Encryption. Encrypt your emails with GnuPG, OpenPGP, S/MIME or your favourite email client. Keep your secret keys secure on your Nitrokey'. There are more than 10 alternatives to Nitrokey for a variety of platforms, including Windows, Android, iPhone, Linux and iPad. The best alternative is Authy, which is free. Other great apps like Nitrokey are YubiKey (Paid), Microsoft Authenticator (Free), SoloKeys (Paid, Open Source) and OnlyKey (Paid, Open Source).
- 10 alternatives
- A secure and open source 2 factor authentication token. Designed to be affordable and reliable. View 7 alternatives to U2F Zero
The official website does not exist anymore, and the Github repository's README states the project no longer maintained: https://github.com/conorpp/u2f-zero/blob/master/README.md
- Free • Open Source