move blowfish docs to new weak ciphers section, linkify aes
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 94d58ee..31ceea8 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -107,11 +107,21 @@
``56`` bits long), they can simply be concatenated to
produce the full key. This must be kept secret.
+Weak Ciphers
+------------
+
+.. warning::
+
+ These ciphers are considered weak for a variety of reasons. New
+ applications should avoid their use and existing applications should
+ strongly consider migrating away.
+
.. class:: Blowfish(key)
Blowfish is a block cipher developed by Bruce Schneier. It is known to be
susceptible to attacks when using weak keys. The author has recommended
- that users of Blowfish move to newer algorithms like AES.
+ that users of Blowfish move to newer algorithms like
+ :class:`AES`.
:param bytes key: The secret key, 32-448 bits in length (in increments of
8). This must be kept secret.