diff --git a/CHANGELOG.org b/CHANGELOG.org
index fc50008..0063100 100644
--- a/CHANGELOG.org
+++ b/CHANGELOG.org
@@ -51,3 +51,5 @@
     Add dependencies for API Authentication.
 ** 0.6.0 <2023-08-05 Sat>
     Add User model.
+** 0.7.0 <2023-08-05 Sat>
+    Add the API Authentication.
diff --git a/config/config.exs b/config/config.exs
index e01ef23..cb4bbb8 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -47,6 +47,10 @@ config :logger, :console,
 # Use Jason for JSON parsing in Phoenix
 config :phoenix, :json_library, Jason
 
+config :link_shortener, LinkShortenerWeb.Auth.Guardian,
+  issuer: "link_shortener",
+  secret_key: System.get_env("SECRET_KEY_BASE")
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{config_env()}.exs"
diff --git a/lib/link_shortener_web/auth/guardian.ex b/lib/link_shortener_web/auth/guardian.ex
new file mode 100644
index 0000000..48e1bba
--- /dev/null
+++ b/lib/link_shortener_web/auth/guardian.ex
@@ -0,0 +1,16 @@
+defmodule LinkShortenerWeb.Auth.Guardian do
+  use Guardian, otp_app: :link_shortener
+
+  alias LinkShortener.Accounts
+
+  def subject_for_token(user, _claims) do
+    sub = to_string(user.id)
+    {:ok, sub}
+  end
+
+  def resource_from_claims(claims) do
+    id = claims["sub"]
+    resource = Accounts.get_user!(id)
+    {:ok,  resource}
+  end
+end
diff --git a/lib/link_shortener_web/controllers/api/v1/user_controller.ex b/lib/link_shortener_web/controllers/api/v1/user_controller.ex
index 5b2f807..cf1a7a3 100644
--- a/lib/link_shortener_web/controllers/api/v1/user_controller.ex
+++ b/lib/link_shortener_web/controllers/api/v1/user_controller.ex
@@ -3,41 +3,24 @@ defmodule LinkShortenerWeb.Api.V1.UserController do
 
   alias LinkShortener.Accounts
   alias LinkShortener.Accounts.User
+  alias LinkShortenerWeb.Auth.Guardian
 
   action_fallback LinkShortenerWeb.FallbackController
 
-  def index(conn, _params) do
-    users = Accounts.list_users()
-    render(conn, "index.json", users: users)
-  end
-
   def create(conn, %{"user" => user_params}) do
-    with {:ok, %User{} = user} <- Accounts.create_user(user_params) do
+    with {:ok, %User{} = user} <- Accounts.create_user(user_params),
+	 {:ok, token, _claims} <- Guardian.encode_and_sign(user) do
       conn
       |> put_status(:created)
-      |> put_resp_header("location", Routes.v1_user_path(conn, :show, user))
-      |> render("show.json", user: user)
+      |> render("user.json", %{user: user, token: token})
     end
   end
 
-  def show(conn, %{"id" => id}) do
-    user = Accounts.get_user!(id)
-    render(conn, "show.json", user: user)
-  end
-
-  def update(conn, %{"id" => id, "user" => user_params}) do
-    user = Accounts.get_user!(id)
-
-    with {:ok, %User{} = user} <- Accounts.update_user(user, user_params) do
-      render(conn, "show.json", user: user)
-    end
-  end
-
-  def delete(conn, %{"id" => id}) do
-    user = Accounts.get_user!(id)
-
-    with {:ok, %User{}} <- Accounts.delete_user(user) do
-      send_resp(conn, :no_content, "")
+  def signin(conn, %{"email" => email, "password" => password}) do
+    with {:ok, user, token} <- Guardian.authenticate(email, password) do
+      conn
+      |> put_status(:created)
+      |> render("user.json", %{user: user, token: token})
     end
   end
 end
diff --git a/lib/link_shortener_web/router.ex b/lib/link_shortener_web/router.ex
index 303d7ff..db4401d 100644
--- a/lib/link_shortener_web/router.ex
+++ b/lib/link_shortener_web/router.ex
@@ -27,6 +27,8 @@ defmodule LinkShortenerWeb.Router do
 
     scope "/v1", Api.V1, as: :v1 do
       resources "/links", LinkController
+      post "/users/signup", UserController, :create
+      post "/users/signin", UserController, :signin
     end
   end
 
diff --git a/lib/link_shortener_web/views/api/v1/user_view.ex b/lib/link_shortener_web/views/api/v1/user_view.ex
index 5ed9ac0..dafa1f7 100644
--- a/lib/link_shortener_web/views/api/v1/user_view.ex
+++ b/lib/link_shortener_web/views/api/v1/user_view.ex
@@ -1,20 +1,12 @@
 defmodule LinkShortenerWeb.Api.V1.UserView do
   use LinkShortenerWeb, :view
-  alias LinkShortenerWeb.UserView
 
-  def render("index.json", %{users: users}) do
-    %{data: render_many(users, UserView, "user.json")}
-  end
-
-  def render("show.json", %{user: user}) do
-    %{data: render_one(user, UserView, "user.json")}
-  end
+  alias LinkShortenerWeb.Api.V1.UserView
 
-  def render("user.json", %{user: user}) do
+  def render("user.json", %{user: user, token: token}) do
     %{
-      id: user.id,
       email: user.email,
-      encrypted_password: user.encrypted_password
+      token: token
     }
   end
 end