Auth[1] is an authenticator app available for Android[2][3][4], iOS[5] and web[6], that provides E2EE backups for your 2FA secrets.
The app also offers an offline mode, that works just as well, minus the E2EE sync.
It's built on the same cryptography primitives as our Photos app, that has been externally audited[7].
We built Auth because we couldn't find a cross-platform, open source app that offered backups. The service is free because costs are negligible, and it helps spread the word about Ente.
If you could check out the product and let us know what we could do better, we'd be grateful!
Best,
[1]: https://github.com/ente-io/auth
[2]: https://play.google.com/store/apps/details?id=io.ente.auth
[3]: https://f-droid.org/en/packages/io.ente.auth/
[4]: https://github.com/ente-io/auth/releases/
[5]: https://apps.apple.com/us/app/ente-authenticator/id6444121398
[6]: https://auth.ente.io
[7]: https://ente.io/blog/cryptography-audit/