2FAS

Two-factor authentication puts a second check on top of a password, and 2FAS is the free app that supplies it. This repository holds the official Android client for the Open Source 2FAS project, showing the one-time code that proves you hold the phone as well as the password.

It implements the two standard algorithms rather than a proprietary scheme, which is what makes it a drop-in for accounts you already have. Any service supporting TOTP or HOTP works with it, Google, Microsoft and Dropbox among them, and setup is a matter of following the on-screen instructions once the app is installed.

A few things are worth knowing before adopting it.

• TOTP: time-based one-time passwords, the algorithm most services use.
• HOTP: counter-based one-time passwords, for services that use those instead.
• Graphics licensing: the artwork in the app is not part of the open source project and carries separate terms.
• Security reports: vulnerabilities go to a dedicated security address rather than the public issue tracker.
• Funding: development and maintenance are supported by donations rather than a paid tier.

Builds are downloaded from the project's releases page and installed on the device. Bug reports go through GitHub issues, where searching for an existing report first is requested, and a contribution guide covers pull requests. The code is licensed under GPL-3.0 by Two Factor Authentication Service, Inc. It suits anyone who wants an authenticator whose source they can read, rather than one tied to an account they do not control.