(Java) Google Authenticator Algorithm

Example code implementing the Google Authenticator algorithm.

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux Java Libs for Android

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Generating TOTP Base32 Secret: 
    // When you enable 2FA with a TOTP-based authenticator app, Google will provide you with a QR code
    // that you can scan using the app. This QR code contains a TOTP base32 secret.
    // You can also choose to view and copy the secret manually.

    String secretBase32 = "JBSWY3DPEHPK3PXP";

    // Do the following to calculate the 6-digit decimal Google authenticator token for a base32 secret,
    // given the current system date/time.
    CkCrypt2 crypt = new CkCrypt2();
    String otp = crypt.totp(secretBase32,"base32","0","",30,6,-1,"sha1");

    System.out.println("6-digit decimal token = " + otp);
  }
}