Add Fast Crypto (TgCrypto) docs

docs/source/index.rst

@@ -63,6 +63,9 @@ Features
     `MTProto Mobile Protocol v2.0`_ and the mechanisms needed for establishing
     a reliable connection.
 
+-   **Fast**: Pyrogram's speed is boosted up by `TgCrypto`_, a high-performance, easy-to-install
+    crypto library written in C.
+
 -   **Updated**: Pyrogram makes use of the latest Telegram API version, currently `Layer 75`_.
 
 -   **Documented**: Pyrogram API public methods are documented and resemble the well
@@ -105,6 +108,7 @@ To get started, press Next.
     resources/ErrorHandling
     resources/ProxyServer
     resources/AutoAuthorization
+    resources/FastCrypto
 
 .. toctree::
     :hidden:
@@ -121,4 +125,6 @@ To get started, press Next.
 
 .. _`MTProto Mobile Protocol v2.0`: https://core.telegram.org/mtproto
 
+.. _TgCrypto: https://docs.pyrogram.ml/resources/FastCrypto/
+
 .. _`Layer 75`: https://github.com/pyrogram/pyrogram/blob/master/compiler/api/source/main_api.tl

docs/source/resources/FastCrypto.rst

@@ -0,0 +1,37 @@
+Fast Crypto
+===========
+
+Pyrogram's speed can be *dramatically* boosted up by installing TgCrypto_, a high-performance, easy-to-install crypto
+library specifically written in C for Pyrogram [#f1]_. TgCrypto is a replacement for the painfully slow PyAES and
+implements the required crypto algorithms MTProto requires, namely AES-IGE and AES-CTR 256 bit.
+
+Installation
+------------
+
+.. code-block:: bash
+
+    $ pip install --upgrade tgcrypto
+
+
+.. note:: Being a C extension for Python, TgCrypto is an optional but *highly recommended* dependency; when TgCrypto
+   is not detected on your system, Pyrogram will automatically fall back to PyAES and will show you a warning.
+
+The reason about being an optional package is that TgCrypto requires some extra system tools in order to be compiled.
+Usually the errors you receive when trying to install TgCrypto are enough to understand what you should do next.
+
+-  **Windows**: Install `Visual C++ 2015 Build Tools <http://landinghub.visualstudio.com/visual-cpp-build-tools>`_.
+
+-  **macOS**: A pop-up will automatically ask you to install the command line developer tools as soon as you issue the
+   installation command.
+
+-  **Linux**: Depending on your distro, install a proper C compiler (``gcc``, ``clang``) and the Python header files
+   (``python3-dev``).
+
+-  **Termux (Android)**: Install ``clang`` and ``python-dev`` packages.
+
+More help on the `Pyrogram group chat <https://t.me/PyrogramChat>`_.
+
+.. _TgCrypto: https://github.com/pyrogram/tgcrypto
+
+.. [#f1] Although TgCrypto is intended for Pyrogram, it is shipped as a standalone package and can thus be used for
+   other projects too.