(Objective-C) Google Authenticator Algorithm

Example code implementing the Google Authenticator algorithm.

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#import <NSString.h>
#import <CkoCrypt2.h>

// 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.

NSString *secretBase32 = @"JBSWY3DPEHPK3PXP";

// Do the following to calculate the 6-digit decimal Google authenticator token for a base32 secret,
// given the current system date/time.
CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];
NSString *otp = [crypt Totp: secretBase32 secretEnc: @"base32" t0: @"0" tNow: @"" tStep: [NSNumber numberWithInt: 30] numDigits: [NSNumber numberWithInt: 6] truncOffset: [NSNumber numberWithInt: -1] hashAlg: @"sha1"];

NSLog(@"%@%@",@"6-digit decimal token = ",otp);