Google Authenticator is based on RFC 4226 - a Time based One Time Password (TOTP) which is initialised using a 16 digit base 32 (RFC 4648) encoded seed value. Initial seeds used for the TOTP can be entered into the Google Authenticator via a camera using QR codes or via the keyboard.

This Repository contains the working functions and all dependencies to either create a token generator or to validate tokens.

The code in previous versions of the Base32U.pas was not even close to being unicode ready. If you found this repository while looking for a working Base32 Implementation in Delphi, please have a look at SZCodeBaseX. To have that one working in Delphi XE2 and higher, you will have to replace all String-Arguments with AnsiString ones.

MYBASE32SECRET is the pre-shared secret.

uses
  GoogleOTP;
  
[...]

var
	Token: Integer;
begin
	// Using time-based Token
	Token := CalculateOTP('MYBASE32SECRET'); // Returns the Token as Integer;

	// To display the token, use the Format-Function
	ShowMessage(Format('%.6d', [Token]));
end;

MYBASE32SECRET is the pre-shared secret. 4 is an example value from the counter

uses
  GoogleOTP;
  
[...]

var
	Token: Integer;
begin
	// Using counter-based Token
	Token := CalculateOTP('MYBASE32SECRET', 4); // Returns the Token as Integer;

	// To display the token, use the Format-Function
	ShowMessage(Format('%.6d', [Token]));
end;

uses
  GoogleOTP;
  
[...]

var
	Token: Integer;
begin
	// Ask the user for a token
	Token := 123456;
	
	// Check the Token
	if (ValidateTOPT('MYBASE32SECRET', Token)) then
		ShowMessage('Access granted')
	else
		ShowMessage('Access denied');
end;

This repository is licensed under the MIT license.