Generate one time passwords, HOTPs based on RFC 4226 and TOTPs based on RFC 6238 for your application. Should work with the Google Authenticator.
Get a HTOP based on a counter:
(hotp secret counter)Get a TOTP based on the time:
(totp secret)Get a HOTP based QR code image url:
(hotp-url label counter secret)Get a TOTP based QR code image url:
(totp-url label secret)Check the LICENCE file.