Google Authenticator TOTP Default Algorithm: A Key to Unlocking Secure Authentication

Google Authenticator is a widely used time-based one-time password (TOTP) solution that offers an extra layer of security for online accounts. The TOTP is generated using a software token on a mobile device, which is synchronized with the server to produce a single-use code with a finite lifetime.

One of the most important aspects of Google Authenticator is the algorithm used to generate the TOTP. By default, the algorithm is set to SHA1, which has been widely adopted across various platforms and apps. However, some users may want to use alternative algorithms, such as SHA256, for added security.

The Issue with Default Algorithm

When trying to create a QR code containing the algorithm written in capital letters (SHA256), most apps, including Microsoft Authenticator and Google Authenticator, fail to generate the correct OTP codes. This is because the default algorithm used by these apps is SHA1, which does not support SHA256.

The Solution: Using Uppercase Algorithm

To use the SHA256 algorithm with Google Authenticator and similar apps, it is essential to create a QR code string containing the uppercase algorithm name (SHA256). This can be done by selecting the TOTP token with the sha256 algorithm in the privacyIDEA authenticator.

Steps to Reproduce the Issue

1. Create a QR code string using the SHA256 algorithm.

2. Scan the QR code with Google Authenticator or similar apps.

3. Select the TOTP token with the sha256 algorithm.

4. Verify that the app generates the correct OTP codes.

In conclusion, while Google Authenticator offers an excellent solution for secure authentication, it is crucial to understand the default algorithm used and how to switch to alternative algorithms like SHA256 for added security. By following these steps and using uppercase algorithm names, users can ensure seamless integration with various apps and platforms.

Google authenticator totp default algorithm