Two (2) Factor Authentication (2FA) Java Code

2 Factor Authentication (2FA) Java code which used the Time-based One-time Password (TOTP) algorithm. You can use this code with the Google Authenticator mobile app or the Authy mobile or browser app.

• See the wikipedia page about TOTP.
• Code available from the git repository.
• Maven packages are published via

To get this to work you:

1. Use generateBase32Secret() to generate a secret key in base-32 format for the user. For example: "NY4A5CPJZ46LXZCP"
2. Store the secret key in the database associated with the user account.
3. Display the QR image URL returned by qrImageUrl(...) to the user. Here's a sample which uses GoogleAPIs:
   
4. User uses the image to load the secret key into his authenticator application.

Whenever the user logs in:

1. The user enters the number from the authenticator application into the login form on the web server.
2. The web server reads the secret associated with the user account from the database.
3. The server compares the user input with the output from generateCurrentNumberString(...).
4. If they are equal then the user is allowed to log in.

For more details, see the example program.

ChangeLog Release Notes

See the ChangeLog.txt file.