diff --git a/lib/chess/auth/auth.ex b/lib/chess/auth/auth.ex
new file mode 100644
index 0000000..44a0c39
--- /dev/null
+++ b/lib/chess/auth/auth.ex
@@ -0,0 +1,114 @@
+defmodule Chess.Auth do
+  @moduledoc """
+  The Auth context.
+  """
+
+  import Ecto.Query, warn: false
+  alias Comeonin.Argon2
+  alias Chess.Repo
+
+  alias Chess.Auth.User
+
+  @doc """
+  Returns the list of users.
+
+  ## Examples
+
+      iex> list_users()
+      [%User{}, ...]
+
+  """
+  def list_users do
+    Repo.all(User)
+  end
+
+  @doc """
+  Gets a single user.
+
+  Raises `Ecto.NoResultsError` if the User does not exist.
+
+  ## Examples
+
+      iex> get_user!(123)
+      %User{}
+
+      iex> get_user!(456)
+      ** (Ecto.NoResultsError)
+
+  """
+  def get_user!(id), do: Repo.get!(User, id)
+
+  @doc """
+  Creates a user.
+
+  ## Examples
+
+      iex> create_user(%{field: value})
+      {:ok, %User{}}
+
+      iex> create_user(%{field: bad_value})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def create_user(attrs \\ %{}) do
+    %User{}
+    |> User.changeset(attrs)
+    |> Repo.insert()
+  end
+
+  @doc """
+  Updates a user.
+
+  ## Examples
+
+      iex> update_user(user, %{field: new_value})
+      {:ok, %User{}}
+
+      iex> update_user(user, %{field: bad_value})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def update_user(%User{} = user, attrs) do
+    user
+    |> User.changeset(attrs)
+    |> Repo.update()
+  end
+
+  @doc """
+  Deletes a User.
+
+  ## Examples
+
+      iex> delete_user(user)
+      {:ok, %User{}}
+
+      iex> delete_user(user)
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def delete_user(%User{} = user) do
+    Repo.delete(user)
+  end
+
+  @doc """
+  Returns an `%Ecto.Changeset{}` for tracking user changes.
+
+  ## Examples
+
+      iex> change_user(user)
+      %Ecto.Changeset{source: %User{}}
+
+  """
+  def change_user(%User{} = user) do
+    User.changeset(user, %{})
+  end
+
+  @doc false
+  def authenticate_user(username, password) do
+    Repo.one(
+      from u in User,
+      where: u.username == ^username
+    )
+    |> Argon2.check_pass(password)
+  end
+end
diff --git a/lib/chess/auth/guardian.ex b/lib/chess/auth/guardian.ex
new file mode 100644
index 0000000..db981ad
--- /dev/null
+++ b/lib/chess/auth/guardian.ex
@@ -0,0 +1,17 @@
+defmodule Chess.Auth.Guardian do
+  use Guardian, otp_app: :auth_ex
+
+  alias Chess.Auth
+
+  def subject_for_token(user, _claims) do
+    {:ok, to_string(user.id)}
+  end
+
+  def resource_from_claims(claims) do
+    user = claims["sub"]
+    |> Auth.get_user!
+    {:ok, user}
+
+    # If something goes wrong here return {:error, reason}
+  end
+end
diff --git a/lib/chess/auth/user.ex b/lib/chess/auth/user.ex
new file mode 100644
index 0000000..2624306
--- /dev/null
+++ b/lib/chess/auth/user.ex
@@ -0,0 +1,32 @@
+defmodule Chess.Auth.User do
+  @moduledoc false
+
+  use Ecto.Schema
+  import Ecto.Changeset
+  alias Chess.Auth.User
+  alias Comeonin.Argon2
+
+  schema "users" do
+    field :password, :string, virtual: true
+    field :password_hash, :string
+    field :username, :string
+
+    timestamps()
+  end
+
+  @doc false
+  def changeset(%User{} = user, attrs) do
+    user
+    |> cast(attrs, [:username, :password])
+    |> validate_required([:username, :password])
+    |> hash_password()
+  end
+
+  defp hash_password(
+    %Ecto.Changeset{valid?: true, changes: %{password: password}} = changeset
+  ) do
+    change(changeset, Argon2.add_hash(password))
+  end
+
+  defp hash_password(changeset), do: changeset
+end
diff --git a/priv/repo/migrations/20180115230143_create_users.exs b/priv/repo/migrations/20180115230143_create_users.exs
new file mode 100644
index 0000000..1d1b1ff
--- /dev/null
+++ b/priv/repo/migrations/20180115230143_create_users.exs
@@ -0,0 +1,12 @@
+defmodule Chess.Repo.Migrations.CreateUsers do
+  use Ecto.Migration
+
+  def change do
+    create table(:users) do
+      add :username, :string
+      add :password_hash, :string
+
+      timestamps()
+    end
+  end
+end
diff --git a/test/chess/auth/auth_test.exs b/test/chess/auth/auth_test.exs
new file mode 100644
index 0000000..4d2dc03
--- /dev/null
+++ b/test/chess/auth/auth_test.exs
@@ -0,0 +1,65 @@
+defmodule Chess.AuthTest do
+  use Chess.DataCase
+
+  alias Chess.Auth
+
+  describe "users" do
+    alias Chess.Auth.User
+
+    @valid_attrs %{password: "some password", username: "some username"}
+    @update_attrs %{password: "some updated password", username: "some updated username"}
+    @invalid_attrs %{password: nil, username: nil}
+
+    def user_fixture(attrs \\ %{}) do
+      {:ok, user} =
+        attrs
+        |> Enum.into(@valid_attrs)
+        |> Auth.create_user()
+
+      user
+    end
+
+    test "list_users/0 returns all users" do
+      user = user_fixture()
+      assert Auth.list_users() == [user]
+    end
+
+    test "get_user!/1 returns the user with given id" do
+      user = user_fixture()
+      assert Auth.get_user!(user.id) == user
+    end
+
+    test "create_user/1 with valid data creates a user" do
+      assert {:ok, %User{} = user} = Auth.create_user(@valid_attrs)
+      assert user.username == "some username"
+    end
+
+    test "create_user/1 with invalid data returns error changeset" do
+      assert {:error, %Ecto.Changeset{}} = Auth.create_user(@invalid_attrs)
+    end
+
+    test "update_user/2 with valid data updates the user" do
+      user = user_fixture()
+      assert {:ok, user} = Auth.update_user(user, @update_attrs)
+      assert %User{} = user
+      assert user.username == "some updated username"
+    end
+
+    test "update_user/2 with invalid data returns error changeset" do
+      user = user_fixture()
+      assert {:error, %Ecto.Changeset{}} = Auth.update_user(user, @invalid_attrs)
+      assert user == Auth.get_user!(user.id)
+    end
+
+    test "delete_user/1 deletes the user" do
+      user = user_fixture()
+      assert {:ok, %User{}} = Auth.delete_user(user)
+      assert_raise Ecto.NoResultsError, fn -> Auth.get_user!(user.id) end
+    end
+
+    test "change_user/1 returns a user changeset" do
+      user = user_fixture()
+      assert %Ecto.Changeset{} = Auth.change_user(user)
+    end
+  end
+end