Time-based One-Time Passwords (TOTP) with the HMAC-SHA-1, HMAC-SHA-256 and HMAC-SHA-512 algorithms.

They are single-use codes used for 2-Factor Authentication.

import Chronos (Timespan, now, second)
import Data.ByteString.Base32 qualified as Base32
import Data.Maybe (fromJust)
import Data.Text (Text)
import OTP.Commons
import OTP.TOTP
import Sel.HMAC.SHA256 qualified as HMAC
import Torsor (scale)

period :: Timespan
period = scale 30 second

sixDigits :: Digits
sixDigits = fromJust $ mkDigits 6

uriFromKey :: Text -> Text -> HMAC.AuthenticationKey -> Text
uriFromKey domain email key =
 let
   issuer = "your-domain"
  in
   totpToURI
     (Base32.encodeBase32Unpadded $ HMAC.unsafeAuthenticationKeyToBinary key)
     email
     issuer
     sixDigits
     period
     HMAC_SHA1

validateTOTP :: HMAC.AuthenticationKey -> Text -> IO Bool
validateTOTP key code = do
 timestamp <- now
 pure $
   totpSHA1Check
     key
     (1, 1)
     timestamp
     period
     sixDigits
     code