QR Code Encoder

Reference used was ISO/IEC 18004, 1st Edition (2000)

This implementation is informed by my specific needs, i.e. to provide two-factor authentication for mobile phones running Google Authenticator.

• "Byte" mode only (don't need e.g. numeric mode or kanji mode).
• Encode only (no detection/decode).
• Basic supporting library functions provided (HOTP, PNG image functions) to allow full-cyle demo.

Demo

1. Download repo and compile with erl -make
2. Install Google Authenticator App on your mobile:
   • iPhone: http://itunes.apple.com/us/app/google-authenticator/id388497605?mt=8
   • Android: https://market.android.com/details?id=com.google.android.apps.authenticator
3. Run demo: qrcode_demo:run().
4. Open the generated qrcode.png file
5. Scan the qrcode into the phone.
6. Ensure server clock is correct.
7. The value of qrcode_demo:totp() should show the same passcode as the phone.
8. Handle PINs/logins for the second part of the "two factor" according to your application design.

NOTE: This documentation is rather basic as this was open-sourced by specific request!

How to use QR Code Encoder with Elixir

Add :qrcode to mix.deps ::

defp deps do
  [{:qrcode, git: “git@gitlab.com:Pacodastre/qrcode.git”}]
end

Then run: ::

mix deps.get
mix deps.compile

Then, whenever you have this compiled, you should have access to the functions available in elixir.

iex(1)> qrcode = :qrcode.encode(“bla”)
{:qrcode, 1, :M, 29,
 <<0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 254, 211, 248, 4, 16, 208, 64, 46, 152, ...>>}
 iex(2)> png = :qrcode_demo.simple_png_encode(qrcode)
 <<137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 232, 0, 0, 0, ...>>
 iex(3)> :file.write_file(“example.png”, png)
 :ok