TOTP

Elm implementation of RFC6238.

You can use this library with pablohirafuji/elm-qrcode to generate a QR code for your user to setup their OTP authenticator devices.

You can also use this library in the backendn (for example choonkeat/elm-webapp) to verify if a user input matches their OTP.

1. Initialize a Key

   keyResult : Result String TOTP.Key.Key
   keyResult =
       TOTP.Key.init
           { issuer = "ACME Co"
           , user = "[email protected]"
           , rawSecret = "topsecret"
           , outputLength = Nothing
           , periodSeconds = Nothing
           , algorithm = TOTP.Algorithm.SHA1
           }

2. And generate a QR code using pablohirafuji/elm-qrcode

   view : TOTP.Key.Key -> Html msg
   view key =
       QRCode.fromString (TOTP.Key.toString key)
           |> Result.map (QRCode.toSvg [])
           |> Result.withDefault (text "Error while encoding to QRCode.")

3. Check if a user input String matches the OTP code

   TOTP.Key.code now key == inputString

4. Save Key into your database by converting it into a String first

   TOTP.Key.toString key

5. Load Key from your database,

   TOTP.Key.fromString key

See the code in example. The running example instance can be found at elm-totp.netlify.app