While I'm not sure what each implementation does, this popular Java implementation of Google Authenticator indeed generates a key with 10 bytes: https://github.

While I'm not sure what each implementation does, this popular Java implementation of Google Authenticator indeed generates a key with 10 bytes: https://github.com/wstrange/GoogleAuth/blob/d5074b49420132776c770ba1277a4df158e7398f/src/main/java/com/warrenstrange/googleauth/GoogleAuthenticator.java#L103 https://github.com/wstrange/GoogleAuth/blob/d5074b4942013277...