# TwoFactorInACan

`TwoFactorInACan` is a library for adding two factor authentication (2FA) to
your application. Its goal is to be the most developer friendly way to securely
setup two factor authentication in the Elixir/Erlang ecosystem. That means that
not only is it thoroughly documented and easy to add to your project, but it's
also the easiest to understand should you need to take a look behind the
curtain.

See the [Official Documentation](https://hexdocs.pm/two_factor_in_a_can) for
details on usage!

Documentation is not yet up at hexdocs, because it has not been released.

## Roadmap

This project is still very, very, very much under construction.

That said, here's what's planned:
- [ ] HMAC based One Time Password 2FA (HOTP)
  - [x] Secret Generation
  - [x] `Hotp.generate_token/3` function
  - [x] `Hotp.same_secret?/3` function
  - [ ] Write documentation
- [x] Time-based One Time Password 2FA (TOTP)
  - [x] Secret Generation
  - [x] `Totp.current_token_value/2` function
  - [x] `Totp.same_secret?/3` function
  - [x] Write documentation
- [ ] Easy TOTP QR Code generation
  - [ ] with nonce
  - [ ] with sha256
- [ ] Universal Second Factor (U2P)
- [ ] Add examples to `README.md`
- [ ] Tutorial for adding to Phoenix

### Maybe, but probably not

2FA via text to someone's phone (SMS) is better than no 2FA at all, but there
are security users to be aware of. The main one is that it is not impossible to
intercept the communication of the token when sent to the user's phone number.
Ultimately, there are no cryptographic guarantees that the device used to
authenticate is the same device that was originally used to setup 2FA.

- [ ] SMS based 2FA
  - [ ] Thoroughly warn about not using
    - [ ] But note why its still better than no 2FA at all
  - [ ] Build OTP process tree for keeping state of recently sent SMS
  - [ ] `Sms.generate_and_send_token/2` function
  - [ ] `Sms.verify_token/3` function
  - [ ] Document to pieces

## Installation

This library is not currently available on hex.

Once it is:

The package can be installed by adding `two_factor_in_a_can` to your list of
dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:two_factor_in_a_can, "~> 0.1.0"}
  ]
end
```