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Checkout the Coherence Demo Project to see an example project using Coherence.

Coherence is a full featured, configurable authentication system for Phoenix, with the following modules:

  • Database Authenticatable: handles hashing and storing an encrypted password in the database.
  • Invitable: sends invites to new users with a sign-up link, allowing the user to create their account with their own password.
  • Registerable: allows anonymous users to register a users email address and password.
  • Confirmable: new accounts require clicking a link in a confirmation email.
  • Recoverable: provides a link to generate a password reset link with token expiry.
  • Trackable: saves login statistics like login counts, timestamps, and IP address for each user.
  • Lockable: locks an account when a specified number of failed sign-in attempts has been exceeded.
  • Unlockable With Token: provides a link to send yourself an unlock email.
  • Rememberable: provides persistent login with 'Remember me?' check box on login page.

Coherence provides flexibility by adding namespaced templates and views for only the options specified by the mix coh.install command. This boiler plate code is added to your lib/my_project/web/templates/coherence and lib/my_project/web/views/coherence directories.

Once the boilerplate has been generated, you are free to customize the source as required.

As well, a lib/my_project/web/coherence_web.ex is added. Migrations are also generated to add the required database fields.

See the Docs and Wiki for more information.


  1. Add coherence to your list of dependencies in mix.exs:

     def deps do
       [{:coherence, "~> 0.8"}]
  2. Ensure coherence is started before your application:

     def application do
       extra_applications: [..., :coherence]]


After upgrading a Coherence version, you should generate the boilerplate files. To assist this process, use the --reinstall option.

This option uses your project's existing coherence config and runs the the installer with the same options.

mix coh.install --reinstall

Run a git diff to review the updated files. If you had updated any of the boilerplate files, you may need to manually integrate the changes into the newly generated files.

Run mix help coh.install for more information.

Phoenix & Phx Project Structure

Coherence supports projects created with the older mix and the newer mix commands. Separate versions of the mix tasks exist for each project structure.

For projects created with mix, use the following mix tasks:

  • coh.install
  • coh.clean

For projects created with mix --umbrella, ensure you are in the app directory and use the following options for the install:

  • cd apps/my_project
  • coh.install --web-module MyProjectWeb --web-path ../my_project_web/lib/my_project_web

Getting Started

First, decide which modules you would like to use for your project. For the following example we are going to use a full install except for the confirmable option.

Run the installer

$ mix coh.install --full-invitable

This will:

  • add the coherence configuration to the end of your config/config.exs file.
  • add a new User model if one does not already exist
  • add migration files
    • timestamp_add_coherence_to_user.exs if the User model already exists
    • timestamp_create_coherence_user.exs if the User model does not exist
    • timestamp_create_coherence_invitable.exs
  • add view files lib/my_project/web/views/coherence/
  • add template files to lib/my_project/web/templates/coherence
  • add email files to lib/my_project/web/emails/coherence
  • add lib/my_project/web/coherence_web.ex file
  • add lib/my_project/web/coherence_messages.ex file

You should review your config/config.exs as there are a couple items you will need to customize like email address and mail api_key. If you don't edit the email_from value to something different than its default, emails may not be sent.

See Installer for more install options.

You will need to update a few files manually.

# lib/my_project_web/router.ex

defmodule MyProjectWeb.Router do
  use MyProjectWeb, :router
  use Coherence.Router         # Add this

  pipeline :browser do
    plug :accepts, ["html"]
    plug :fetch_session
    plug :fetch_flash
    plug :protect_from_forgery
    plug :put_secure_browser_headers
    plug Coherence.Authentication.Session  # Add this

  # Add this block
  pipeline :protected do
    plug :accepts, ["html"]
    plug :fetch_session
    plug :fetch_flash
    plug :protect_from_forgery
    plug :put_secure_browser_headers
    plug Coherence.Authentication.Session, protected: true

  # Add this block
  scope "/" do
    pipe_through :browser

  # Add this block
  scope "/" do
    pipe_through :protected
    coherence_routes :protected

  scope "/", MyProjectWeb do
    pipe_through :browser

    get "/", PageController, :index
    # add public resources below

  scope "/", MyProjectWeb do
    pipe_through :protected

    # add protected resources below
    resources "/privates", MyProjectWeb.PrivateController

Important: Note the name-spacing above. Unless you generate coherence controllers, ensure that the scopes, scope "/" do, do not include your projects' scope here. If so, the coherence routes will not work!

If the installer created a user schema (one did not already exist), there is nothing you need to do with that generated file. Otherwise, update your existing schema (assuming its Accounts.User like this:

# lib/my_project/accounts/user.ex

defmodule MyProject.Accounts.User do
  use Ecto.Schema
  use Coherence.Schema                                    # Add this

  schema "users" do
    field :name, :string
    field :email, :string
    coherence_schema()                                    # Add this


  def changeset(model, params \\ %{}) do
    |> cast(params, [:name, :email] ++ coherence_fields)  # Add this
    |> validate_required([:name, :email])
    |> validate_format(:email, ~r/@/)
    |> validate_coherence(params)                         # Add this

  def changeset(model, params, :password) do
    |> cast(params, ~w(password password_confirmation reset_password_token reset_password_sent_at))
    |> validate_coherence_password_reset(params)

An alternative approach is add the authentication plugs to individual controllers that require authentication. You will want to use this approach if you require authentication for a subset of actions in a controller.

For example, lets say you want to show a list of products for everyone visiting the site, but only want authenticated users to be able to create, update, and delete products. You could do the following:

Ensure the following is in your lib/my_project_web/router.ex file:

scope "/", MyProjectWeb do
  pipe_through :browser
  resources "/products", ProductController

In your product controller add the following:

defmodule MyProjectWeb.ProductController do
  use MyProjectWeb, :controller

  plug Coherence.Authentication.Session, [protected: true] when action != :index

  # ...

Default Configuration

{:require_current_password, true}, # Current password is required when updating new password.
{:reset_token_expire_days, 2},
{:confirmation_token_expire_days, 5},
{:allow_unconfirmed_access_for, 0},
{:max_failed_login_attempts, 5},
{:unlock_timeout_minutes, 20},
{:unlock_token_expire_minutes, 5},
{:rememberable_cookie_expire_hours, 2*24},
{:forwarded_invitation_fields, [:email, :name]}
{:allow_silent_password_recovery_for_unknown_user, false},
{:password_hashing_alg, Comeonin.Bcrypt}

You can override this default configs. For example: you can add the following codes inside config/config.exs

config :coherence,
  require_current_password: false,
  max_failed_login_attempts: 3

Custom registration and sessions routes

Coherence supports custom routes for registration and login. These configurations can be set globally or scoped.

Which routes can be custom?

  registrations_new:  "/registrations/new",
  registrations:      "/registrations",
  passwords:          "/passwords",
  confirmations:      "/confirmations",
  unlocks:            "/unlocks",
  invitations:        "/invitations",
  invitations_create: "/invitations/create",
  invitations_resend: "/invitations/:id/resend",
  sessions:           "/sessions",
  registrations_edit: "/registrations/edit"

To set them globally add the following to you configuration:

config :coherence,
  default_routes: %{
    registrations_edit: "/accounts/edit", ...},

To set them scoped for each mode (protected, public, etc..):

scope "/" do
  pipe_through :protected
  coherence_routes :protected, [
    custom_routes: %{registratons_edit: "/accounts/edit", ...}

Phoenix Channel Authentication

Coherence supports channel authentication using Phoenix.Token. To enable channel authentication do the following:

Add the following option to coherence configuration.

config :coherence,
  user_token: true

Update your socket module:

defmodule MyProjectWeb.UserSocket do
  use Phoenix.Socket

  def connect(%{"token" => token}, socket) do
    case Coherence.verify_user_token(socket, token, &assign/3) do
      {:error, _} -> :error
      {:ok, socket} -> {:ok, socket}

Localization with Gettext

Coherence supports Gettext for all User facing messages. Your project's Gettext module is used by default.

All Coherence messages use dgettext with the "coherence" domain. This means that after you run mix gettext.extract, you will see coherence.pot files generated. Running mix gettext.merge priv/gettext will generate the corresponding coherence.po files.

Coherence does not come with pre-translated .po files. We figure that you will want to tweak the Coherence language to suite your application.

All files added to your project with the Coherence generators include a import MyProjectWeb.Gettext with the "coherence" domain.

The other messages that Coherence uses internal are pulled from the my_project_web/coherence_messages.ex file that is generated with the coh.install mix task. You can edit this file and customize it as required.

To assist in upgrades to future releases of Coherence, the MyProject.Coherence.Messages module uses the Coherence.Messages behaviour which defines each message function. So, if you miss a message after upgrading, you will see a message during compile time.

Option Overview


Handles hashing and storing an encrypted password in the database.

Provides /sessions/new and /sessions/delete routes for logging in and out with the appropriate templates and view.

The following columns are added the <timestamp>_add_coherence_to_user.exs migration:

  • :password_hash, :string - the encrypted password


Handles sending invites to new users with a sign-up link, allowing the user to create their account with their own password.

Provides /invitations/new and invitations/edit routes for creating a new invitation and creating a new account from the invite email.

These routes can be configured to require login by using the coherence_routes :private macro in your router.exs file.

Invitation token timeout will be added in the future.

The following table is created by the generated <timestamp>_create_coherence_invitable.exs migration:

create table(:invitations) do
  add :name, :string
  add :email, :string
  add :token, :string


Allows anonymous users to register a users email address and password.

Provides /registrations/new, create, edit, update, show, and delete routes for managing registrations.

Adds the following:

  • Register New Account to the log-in page.
  • Link to account page on layout helpers
  • Show page with edit and delete links
  • edit page

It is recommended that the :confirmable option is used with :registerable to ensure a valid email address is captured.


Requires a new account be confirmed. During registration, a confirmation token is generated and sent to the registering email. This link must be clicked before the user can sign-in.

Provides edit action for the /confirmations route.

The confirmation token expiry default of 5 days can be changed with the :confirmation_token_expire_days config entry.


Allows users to reset their password using an expiring token send by email.

Provides new, create, edit, update actions for the /passwords route.

Adds a "Forgot your password?" link to the log-in form. When clicked, the user provides their email address and if found, sends a reset password instructions email with a reset link.

The expiry timeout can be changed with the :reset_token_expire_days config entry.

By default, providing an unknown email address will result in a form error. If you want to prevent that and display a confirmation message even if the email isn’t found, set the :allow_silent_password_recovery_for_unknown_user to true.


Saves login statistics like login counts, timestamps, and IP address for each user.

Adds the following database field to your User model with the generated migration:

add :sign_in_count, :integer, default: 0  # how many times the user has logged in
add :current_sign_in_at, :datetime        # the current login timestamp
add :last_sign_in_at, :datetime           # the timestamp of the previous login
add :current_sign_in_ip, :string          # the current login IP adddress
add :last_sign_in_ip, :string             # the IP address of the previous login


Locks an account when a specified number of failed sign-in attempts has been exceeded.

The following defaults can be changed with the following config entries:

  • :unlock_timeout_minutes
  • :max_failed_login_attempts

Adds the following database field to your User model with the generated migration:

add :failed_attempts, :integer, default: 0
add :unlock_token, :string
add :locked_at, :datetime

Unlockable with Token

Provides a link to send yourself an unlock email. When the user clicks the link, the user is presented a form to enter their email address and password. If the token has not expired and the email and password are valid, a unlock email is sent to the user's email address with an expiring token.

The default expiry time can be changed with the :unlock_token_expire_minutes config entry.

Remember Me

The rememberable option provides persistent login when the 'Remember Me?' box is checked during login.

With this feature, you will automatically be logged in from the same browser when your current login session dies using a configurable expiring persistent cookie.

For security, both a token and series number stored in the cookie on initial login. Each new creates a new token, but preserves the series number, providing protection against fraud. As well, both the token and series numbers are hashed before saving them to the database, providing protection if the database is compromised.

The following defaults can be changed with the following config entries:

  • :rememberable_cookie_expire_hours (2*24)
  • :login_cookie ("coherence_login")

The following table is created by the generated <timestamp>_create_coherence_rememberable.exs migration:

create table(:rememberables) do
  add :series_hash, :string
  add :token_hash, :string
  add :token_created_at, :datetime
  add :user_id, references(:users, on_delete: :delete_all)


create index(:rememberables, [:user_id])
create index(:rememberables, [:series_hash])
create index(:rememberables, [:token_hash])
create unique_index(:rememberables, [:user_id, :series_hash, :token_hash])

The --rememberable install option is not provided in any of the installer group options. You must provide the --rememberable option to install the migration and its support.

User Active Field

The --user-active-field option can be given to the installer to support inactive users. When a user is set as inactive, they will not be able to login.

Using this option adds a active field to the user schema with a default of true.

Mix Tasks


The following examples illustrate various configuration scenarios for the install mix task:

# Install with only the `authenticatable` option
$ mix coh.install

# Install all the options except `confirmable` and `invitable`
$ mix coh.install --full

# Install all the options except `invitable`
$ mix coh.install --full-confirmable

# Install all the options except `confirmable`
$ mix coh.install --full-invitable

# Install the `full` options except `lockable` and `trackable`
$ mix coh.install --full --no-lockable --no-trackable

And some reinstall examples:

# Reinstall with defaults (--silent --no-migrations --no-config --confirm-once)
$ mix coh.install --reinstall

# Confirm to overwrite files, show instructions, and generate migrations
$ mix coh.install --reinstall --no-confirm-once --with-migrations

Run $ mix help coh.install for more information.


The following examples illustrate how to remove the files created by the installer:

# Clean all the installed files
$ mix coh.clean --all

# Clean only the installed view and template files
$ mix coh.clean --views --templates

# Clean all but the models
$ mix coh.clean --all --no-models

# Prompt once to confirm the removal
$ mix coh.clean --all --confirm-once

After installation, if you later want to remove one more options, here are a couple examples:

# Clean one option
$ mix coh.clean --options=recoverable

# Clean several options without confirmation
$ mix coh.clean --no-confirm --options="recoverable unlockable-with-token"

# Test the uninstaller without removing files
$ mix coh.clean --dry-run --options="recoverable unlockable-with-token"


The coh.install mix task generates a bunch of boiler plate code so you can easily customize the views, templates, and mailer.

Also, checkout the Coherence.Config module for a list of config items you can use to tune the behaviour of Coherence.

Custom Controllers

By default, controller boilerplate is not generated. To add controllers, use the controller generators.

The generated controllers are named MyProjectWeb.Coherence.SessionController as an example. Generated controllers are located in lib/my_project_web/controllers/coherence/

If the controllers are generated, you will need to change your router to use the new names. For example:

# lib/my_project_web/router.ex

defmodule MyProjectWeb.Router do
  use MyProjectWeb, :router
  use Coherence.Router

  # ...

  scope "/", MyProjectWeb do   # note the addition of MyProjectWeb
    pipe_through :public

  scope "/", MyProjectWeb do   # note the addition of MyProjectWeb
    pipe_through :browser
    coherence_routes :protected

  # ...

As of Coherence v0.6.0, the generated controller modules have very little code. All the controller actions and helper functions are included with a use xxxControllerBase call.

To change an action, simply define the appropriate function and add your own implementation. You may want to copy over the implementation found in your projects deps/coherence/lib/coherence/controllers/xxx_controller_base.ex file as a starting point and customize it as needed.

Alternatively, if can create the action, handle some specify behavior and call super(conn, params) so invoke the default action. Depending on your customization, this may be the best approach since its easier to see how changes when upgrading to new versions of Coherence.

Customizing Routes

By default, Coherence assumes you want all available routes for the opts you've configured. However, you can specify which routes should be available by modifying your configuration.

For example, if you want all of the routes for authenticatable, but only the new and create actions from registerable:

# config/config.exs
config :coherence,
  # ...
  opts: [:authenticatable, registerable: [:new, :create]]

Customizing Redirections

Many of the controller actions redirect the user after create and update actions. These redirections can be customized by adding function call backs in the lib/my_project_web/controllers/coherence/redirect.ex module that is generated by the mix coh.install task.

For example, to have the user redirected to the login screen after logging out at the following:

defmodule Coherence.Redirects do
  use Redirects
  import MyProjectWeb.Router.Helpers

  # override the log out action back to the log in page
  def session_delete(conn, _), do: redirect(conn, session_path(conn, :new))

See the documentation for further details.

Customizing Responders

To customize how application responds to html or json format, you can override methods in the lib/my_project_web/controllers/coherence/responders/html.ex or lib/my_project_web/controllers/coherence/responders/json.ex.

Customizing layout

By default coherence uses its own layout which is installed to lib/my_project_web/templates/coherence/layout/app.html.eex.

If you want to customize coherence controllers layout, you can follow different approaches:

  • Edit the generated layout at lib/my_project_web/templates/coherence/layout/app.html.eex.
  • Set :layout in your config file. e.g. config :coherence, :layout, {MyProjectWeb.LayoutView, :app}
  • Install coherence controllers to application and edit them, to use layout module different from Coherence.LayoutView
  • And the last solution is to use plug :put_layout in your lib/my_project_web/router.ex file. For example:
defmodule MyProjectWeb.Router do
  # ...
  pipeline :coherence do
    plug :put_layout, {MyProjectWeb.LayoutView, :app}
  # ...
  scope "/" do
    pipe_through [:protected, :coherence]
    coherence_routes :protected

Customizing User Changeset

The User model changeset used by Coherence can be customized for each Coherence controller. To customize the changeset, set the changeset config option.

For example, the following defines a changeset/3 function in your user model:

# config/config.exs
config :coherence,
  # ...
  changeset: {MyProject.User, :changeset}

Now add a new changeset/3 function to the user model. The following example defines a custom changeset for the registration controller:

# lib/coherence/coherence/user.ex
defmodule CoherenceDemo.User do
  use Ecto.Schema
  use Coherence.Schema

  # ...

  def changeset(model, params \\ %{}) do
    |> cast(params, [:name, :email] ++ coherence_fields)
    |> validate_required([:name, :email])
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_coherence(params)
  def changeset(model, params, :registration) do
    # custom changeset  for registration controller
    |> cast(params, [:name, :email] ++ coherence_fields)
    |> validate_required([:name, :email])
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_coherence(params)
  def changeset(model, params, _which) do
    # use the default changeset for all other coherence controllers
    changeset model, params

When a custom changeset is configured, the changeset function is called with an atom indicating the controller calling the changeset, allowing you to match on specific controllers.

The list of controller actions are:

  • :confirmation
  • :invitation
  • :password
  • :registration
  • :session
  • :unlock

Customizing Password Hashing Algorithm

Coherence uses the Bcrypt algorithm by default for hashing passwords. However, with the update to Comeonin 4.0, you can now change the hashing algorithm.

Comeonin currently supports the following 3 algorithms:

Change the Hashing Algorithm in an Existing Project

To change the default in an existing project (to Argon2 for example), make the following 2 changes:

  • Edit your config/config.exs file add/change the following line:
# config/config.exs
config :coherence,
  # ...
  password_hashing_alg: Comeonin.Argon2,
  # ...
  • add the dependency to mix.exs
  # mix.exs
  defp deps do
      # ...
      {:argon2_elixir, "~> 1.3"}

Change the Hashing Algorithm in an Existing Project

To install Coherence in a new project with the Pbkdf2 hashing algorithm (with the --full option for example):

# mix coh.install --full --password-hashing-alg=Comeonin.Argon2

and add the dependency

  # mix.exs
  defp deps do
      # ...
      {:pbkdf2_elixir, "~> 0.12"}

Speed up Tests and Database Seeding of Users

The default hashing algorithms are setup for production use. They are very slow by design which can cause very slow tests and database seeding in the dev and test environments. To speed this up, you can add the following to you config/dev.exs and/or config/test.exs configuration.


# config/test.exs
config :argon2_elixir,
  t_cost: 1,
  m_cost: 8
config :bcrypt_elixir, log_rounds: 4
config :pbkdf2_elixir, rounds: 1

Note: Only configure the algorithm you have configured!

Accessing the Currently Logged In User

During login, a current version of the user model is cashed in the credential store. During each authentication request, the user model is fetched from the credential store and placed in conn.assigns[:current_user] to avoid a database fetch on each request.

You can access the current user's name in a template like this:

<%= Coherence.current_user_name(@conn) %>

Any of the user model's available data can be accessed this way.

Updating the User Model

If the user model is changed after login, a call to update_login must be done to update the credential store. For example, in your controller update function, call:

Coherence.update_user_login(conn, user)

to update the credential store.

This is not needed for registration update page.

Configuring the Swoosh Email Adapter

The following configuration must be setup to send emails:

config :coherence,
  email_from_name: "Some Name",
  email_from_email: ""

config :coherence, CoherenceDemoWeb.Coherence.Mailer,
  adapter: Swoosh.Adapters.Sendgrid,
  api_key: "SENDGRID_API_KEY"

You may want to configure the email system to use system environment variables.

config :coherence,
  email_from_name: {:system, "NAME"},
  email_from_email: {:system, "EMAIL"}

config :coherence, CoherenceDemoWeb.Coherence.Mailer,
  api_key: {:system, "SENDGRID_API_KEY"}

Permitted Attributes

For security, Coherence restricts what fields of a schema can be created or updated with several configurable permitted attributes settings. When installing a new project these settings are generated in the :coherence Config block.

In the case of an upgrade, the following values will be used when the configuration is not found:

Configuration FieldDefaults
:registration_permitted_attributes["email","name","password", "current_password", "password_confirmation"]
:password_reset_permitted_attributes["reset_password_token","password", "password_confirmation"]


Currently Coherence supports three modes of authentication including HTTP Basic, Session, and Token authentication.

For HTTP Basic and Token authentication, you will need to add the credentials into the Credential Store. This is not required for Session or IpAddress Authentication.

IpAddress authentication is a good solution for server to server rest APIs.

Add HTTP Basic Credentials Example

creds = Coherence.Authentication.Basic.encode_credentials("Admin", "SecretPass")
Coherence.CredentialStore.Server.put_credentials(creds, %{id: "USER_ID_HERE", role: :admin})

Add Token Credentials Example

token = Coherence.Authentication.Token.generate_token
Coherence.CredentialStore.Server.put_credentials(token, %{id: "USER_ID_HERE", role: :admin})

Add IP Credentials Example

Coherence.CredentialStore.Server.put_credentials({127,0,0,1}, %{id: "USER_ID_HERE", role: :admin})

IpAddress authentication does not require this step. Its optional. If the user_data is not found in the credential store, the conn.assigns will not be set.

To add authentication, use on of the following three:

HTTP Basic Plug Example

plug Coherence.Authentication.Basic, realm: "Secret"

The realm parameter is optional and can be omitted. By default "Restricted Area" will be used as realm name. You can also pass the error parameter, which should be a string or a function. If a string is passed, that string will be sent instead of the default message "HTTP Authentication Required" on authentication failure (with status code 401). If a function is passed, that function will be called with one argument, conn.

Token Plug Example

plug Coherence.Authentication.Token, source: :params, param: "auth_token", error: ~s'{"error":"authentication required"}'

The error parameter is optional and is treated as in the example above. The source parameter defines how to retrieve the token from the connection. Currently, the three acceptable values are: :params, :header and :session. Their name is self-explainatory. The param parameter defines the name of the parameter/HTTP header/session key where the token is stored. This should cover most cases, but if retrieving the token is more complex than that, you can pass a tuple for the source parameter. The tuple must be in the form {MyModule, :my_function, ["param1", 42]}. The function must accept a connection as its first argument (which will be injected as the head of the given parameter list) and any other number of parameters, which must be given in the third element of the tuple. If no additional arguments are needed, an empty list must be given.

Session Plug Example

plug Coherence.Authentication.Session, cookie_expire: 10*60*60, login: &MyController.login/1, assigns_key: :authenticated_user

The :cookie_expire value the expire time in seconds. The :login is a fun that will be passed conn if the user is not logged in. Use the :assigns_key to change the default :current_user value.

Note that if you provide a login callback, that you must return halt conn a the end of the function.

IP Address Plug Example

plug Coherence.Authentication.IpAddress, allow: ~w(
plug Coherence.Authentication.IpAddress, allow: ~w(, deny: ~w(

The first example will allow local host and any ip address in the subnet

The second example allows any ip except for localhost.


Coherence is a user management and authentication solution. Support for authorization (access control) can be achieved using another package like Canary.

For an example of using Canary with Coherence, please visit the CoherenceDemo canary branch.


We appreciate any contribution to Coherence. Check our and guides for more information. We usually keep a list of features and bugs in the issue tracker.



coherence is Copyright (c) 2016-2018 E-MetroTel

The source is released under the MIT License.

Check LICENSE for more information.

Much of the authentication plugs code was taken from PlugAuth, Copyright (c) 2014, Bitgamma OÜ