diff --git a/docs/library/index.rst b/docs/library/index.rst
index d5678d37e3..40fe641c86 100644
--- a/docs/library/index.rst
+++ b/docs/library/index.rst
@@ -179,6 +179,7 @@ the following libraries.
    machine.rst
    micropython.rst
    network.rst
+   ucryptolib.rst
    uctypes.rst
 
 
diff --git a/docs/library/ucryptolib.rst b/docs/library/ucryptolib.rst
new file mode 100644
index 0000000000..4b2c45f073
--- /dev/null
+++ b/docs/library/ucryptolib.rst
@@ -0,0 +1,38 @@
+:mod:`ucryptolib` -- cryptographic ciphers
+==========================================
+
+.. module:: ucryptolib
+   :synopsis: cryptographic ciphers
+
+Classes
+-------
+
+.. class:: aes
+
+    .. classmethod:: __init__(key, mode, [IV])
+
+        Initialize cipher object, suitable for encryption/decryption. Note:
+        after initialization, cipher object can be use only either for
+        encryption or decryption. Running decrypt() operation after encrypt()
+        or vice versa is not supported.
+
+        Parameters are:
+
+            * *key* is an encryption/decryption key (bytes-like).
+            * *mode* is:
+
+                * 1 for Electronic Code Book (ECB).
+                * 2 for Cipher Block Chaining (CBC)
+
+            * *IV* is an initialization vector for CBC mode.
+
+    .. method:: encrypt(in_buf, [out_buf])
+
+        Encrypt *in_buf*. If no *out_buf* is given result is returned as a
+        newly allocated `bytes` object. Otherwise, result is written into
+        mutable buffer *out_buf*. *in_buf* and *out_buf* can also refer
+        to the same mutable buffer, in which case data is encrypted in-place.
+
+    .. method:: decrypt(in_buf, [out_buf])
+
+        Like `encrypt()`, but for decryption.