C

Google Authenticator Algorithm

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Example code implementing the Google Authenticator algorithm. C

#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    const char *secretBase32;
    HCkCrypt2 crypt;
    const char *otp;

    // 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.

    secretBase32 = "JBSWY3DPEHPK3PXP";

    // Do the following to calculate the 6-digit decimal Google authenticator token for a base32 secret,
    // given the current system date/time.
    crypt = CkCrypt2_Create();
    otp = CkCrypt2_totp(crypt,secretBase32,"base32","0","",30,6,-1,"sha1");

    printf("6-digit decimal token = %s\n",otp);


    CkCrypt2_Dispose(crypt);

    }