diff --git a/.gitignore b/.gitignore
index e5fd73b..0e34380 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,3 +24,6 @@ kadena-*.tar
 
 # Temporary files, for example, from tests.
 /tmp/
+
+# Dialyzer plt files
+/priv/plts
diff --git a/.tool-versions b/.tool-versions
new file mode 100644
index 0000000..0a8152e
--- /dev/null
+++ b/.tool-versions
@@ -0,0 +1 @@
+elixir 1.13
diff --git a/lib/types/base16_string.ex b/lib/types/base16_string.ex
new file mode 100644
index 0000000..e3d2f7e
--- /dev/null
+++ b/lib/types/base16_string.ex
@@ -0,0 +1,15 @@
+defmodule Kadena.Types.Base16String do
+  @moduledoc """
+  `Base16String` struct definition.
+  """
+
+  @behaviour Kadena.Types.Spec
+
+  @type t :: %__MODULE__{value: String.t()}
+
+  defstruct [:value]
+
+  @impl true
+  def new(str) when is_binary(str), do: %__MODULE__{value: str}
+  def new(_str), do: {:error, :invalid_string}
+end
diff --git a/lib/types/base64_url.ex b/lib/types/base64_url.ex
new file mode 100644
index 0000000..5cfd7b4
--- /dev/null
+++ b/lib/types/base64_url.ex
@@ -0,0 +1,15 @@
+defmodule Kadena.Types.Base64Url do
+  @moduledoc """
+  `Base64Url` struct definition.
+  """
+
+  @behaviour Kadena.Types.Spec
+
+  @type t :: %__MODULE__{url: String.t()}
+
+  defstruct [:url]
+
+  @impl true
+  def new(str) when is_binary(str), do: %__MODULE__{url: str}
+  def new(_str), do: {:error, :invalid_url}
+end
diff --git a/lib/types/base64_urls_list.ex b/lib/types/base64_urls_list.ex
new file mode 100644
index 0000000..7d3782e
--- /dev/null
+++ b/lib/types/base64_urls_list.ex
@@ -0,0 +1,25 @@
+defmodule Kadena.Types.Base64UrlsList do
+  @moduledoc """
+  `Base64UrlsList` struct definition.
+  """
+  alias Kadena.Types.Base64Url
+
+  @behaviour Kadena.Types.Spec
+
+  @type urls :: list(Base64Url.t())
+
+  @type t :: %__MODULE__{list: urls()}
+
+  defstruct list: []
+
+  @impl true
+  def new(urls), do: build_list(%__MODULE__{}, urls)
+
+  @spec build_list(list :: t(), urls :: urls()) :: t()
+  defp build_list(list, []), do: list
+
+  defp build_list(%__MODULE__{list: list}, [%Base64Url{} = url | rest]),
+    do: build_list(%__MODULE__{list: [url | list]}, rest)
+
+  defp build_list(_list, _urls), do: {:error, :invalid_urls}
+end
diff --git a/lib/types/spec.ex b/lib/types/spec.ex
new file mode 100644
index 0000000..238a71b
--- /dev/null
+++ b/lib/types/spec.ex
@@ -0,0 +1,9 @@
+defmodule Kadena.Types.Spec do
+  @moduledoc """
+  Defines base types constructions.
+  """
+
+  @type error :: {:error, atom()}
+
+  @callback new(any()) :: struct() | error()
+end
diff --git a/lib/types/uint8_array.ex b/lib/types/uint8_array.ex
new file mode 100644
index 0000000..263906b
--- /dev/null
+++ b/lib/types/uint8_array.ex
@@ -0,0 +1,25 @@
+defmodule Kadena.Types.Uint8Array do
+  @moduledoc """
+  `Uint8Array` struct definition.
+  """
+
+  @behaviour Kadena.Types.Spec
+
+  @type values :: binary() | list(integer())
+  @type t :: %__MODULE__{value: values}
+
+  defstruct [:value]
+
+  @impl true
+  def new(buffer) when is_binary(buffer), do: %__MODULE__{value: :binary.bin_to_list(buffer)}
+  def new(list) when is_list(list), do: check_list(%__MODULE__{value: list}, list)
+  def new(_value), do: {:error, :invalid_uint8_array}
+
+  @spec check_list(module_list :: t(), values :: list(integer())) :: t()
+  defp check_list(module_list, []), do: module_list
+
+  defp check_list(module_list, [value | rest]) when is_integer(value) and value >= 0,
+    do: check_list(module_list, rest)
+
+  defp check_list(_module_list, _values), do: {:error, :invalid_uint8_array}
+end
diff --git a/test/types/base16_string_test.exs b/test/types/base16_string_test.exs
new file mode 100644
index 0000000..371bdd7
--- /dev/null
+++ b/test/types/base16_string_test.exs
@@ -0,0 +1,23 @@
+defmodule Kadena.Types.Base16StringTest do
+  @moduledoc """
+  `Base16String` struct definition tests.
+  """
+
+  use ExUnit.Case
+
+  alias Kadena.Types.Base16String
+
+  describe "new/1" do
+    test "with a valid string value" do
+      %Base16String{value: "string"} = Base16String.new("string")
+    end
+
+    test "with an invalid atom value" do
+      {:error, :invalid_string} = Base16String.new(:atom)
+    end
+
+    test "with an invalid nil value" do
+      {:error, :invalid_string} = Base16String.new(nil)
+    end
+  end
+end
diff --git a/test/types/base64_url_test.exs b/test/types/base64_url_test.exs
new file mode 100644
index 0000000..860fd39
--- /dev/null
+++ b/test/types/base64_url_test.exs
@@ -0,0 +1,23 @@
+defmodule Kadena.Types.Base64UrlTest do
+  @moduledoc """
+  `Base64Url` struct definition tests.
+  """
+
+  use ExUnit.Case
+
+  alias Kadena.Types.Base64Url
+
+  describe "new/1" do
+    test "with a valid url" do
+      %Base64Url{url: "valid_url"} = Base64Url.new("valid_url")
+    end
+
+    test "with an invalid url" do
+      {:error, :invalid_url} = Base64Url.new(:atom)
+    end
+
+    test "with a nil url" do
+      {:error, :invalid_url} = Base64Url.new(nil)
+    end
+  end
+end
diff --git a/test/types/base64_urls_list_test.exs b/test/types/base64_urls_list_test.exs
new file mode 100644
index 0000000..ac56555
--- /dev/null
+++ b/test/types/base64_urls_list_test.exs
@@ -0,0 +1,25 @@
+defmodule Kadena.Types.Base64UrlsListTest do
+  @moduledoc """
+  `Base64UrlsList` struct definition tests.
+  """
+
+  use ExUnit.Case
+
+  alias Kadena.Types.{Base64Url, Base64UrlsList}
+
+  describe "new/1" do
+    test "with a valid urls list" do
+      base_url = Base64Url.new("valid_url")
+      %Base64UrlsList{list: [base_url, base_url]} = Base64UrlsList.new([base_url, base_url])
+    end
+
+    test "with an invalid urls list" do
+      base_url = Base64Url.new("valid_url")
+      {:error, :invalid_urls} = Base64UrlsList.new([base_url, :atom, base_url])
+    end
+
+    test "with a list of nil" do
+      {:error, :invalid_urls} = Base64UrlsList.new([nil])
+    end
+  end
+end
diff --git a/test/types/uint8_array_test.exs b/test/types/uint8_array_test.exs
new file mode 100644
index 0000000..7d9a520
--- /dev/null
+++ b/test/types/uint8_array_test.exs
@@ -0,0 +1,37 @@
+defmodule Kadena.Types.Uint8ArrayTest do
+  @moduledoc """
+  `Uint8Array` struct definition tests.
+  """
+
+  use ExUnit.Case
+
+  alias Kadena.Types.Uint8Array
+
+  describe "new/1" do
+    test "with a valid buffer" do
+      %Uint8Array{value: [254, 255, 0, 1, 2]} = Uint8Array.new(<<254, 255, 256, 257, 258>>)
+    end
+
+    test "with a valid list" do
+      values_list = [134, 147, 230, 65, 174, 43, 190, 158]
+      %Uint8Array{value: ^values_list} = Uint8Array.new(values_list)
+    end
+
+    test "with a negative value in the list" do
+      {:error, :invalid_uint8_array} = Uint8Array.new([230, -65, 174])
+    end
+
+    test "with an invalid input" do
+      {:error, :invalid_uint8_array} = Uint8Array.new(-5)
+    end
+
+    test "with a nil value" do
+      {:error, :invalid_uint8_array} = Uint8Array.new(nil)
+    end
+
+    test "with an invalid list" do
+      values_list = [134, 147, 230, 65, 174, 43, 190, :atom, 158]
+      {:error, :invalid_uint8_array} = Uint8Array.new(values_list)
+    end
+  end
+end