add CAST5 docs
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 31ceea8..5852dc2 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -107,6 +107,15 @@
``56`` bits long), they can simply be concatenated to
produce the full key. This must be kept secret.
+.. class:: CAST5(key)
+
+ CAST5 (also known as CAST-128) is a block cipher approved for use in the
+ Canadian government by their Communications Security Establishment. It is a
+ variable key length cipher and supports keys from 40-128 bits in length.
+
+ :param bytes key: The secret key, 40-128 bits in length (in increments of
+ 8). This must be kept secret.
+
Weak Ciphers
------------
@@ -126,7 +135,6 @@
:param bytes key: The secret key, 32-448 bits in length (in increments of
8). This must be kept secret.
-
Modes
~~~~~