ctr doc language take 3
diff --git a/docs/primitives/symmetric-encryption.rst b/docs/primitives/symmetric-encryption.rst
index 21421d1..a1f8ba3 100644
--- a/docs/primitives/symmetric-encryption.rst
+++ b/docs/primitives/symmetric-encryption.rst
@@ -77,19 +77,25 @@
reuse an ``initialization_vector`` with
a given ``key``.
+
.. class:: cryptography.primitives.block.modes.CTR(nonce)
+ .. warning::
+
+ Counter mode is not recommended for use with block ciphers that have a
+ block size of less than 128-bits.
+
CTR (Counter) is a mode of operation for block ciphers. It is considered
cryptographically strong.
- :param bytes nonce: Must be random bytes. They do not need to be kept
- secret (they can be included in a transmitted
- message). Must be the same number of bytes as the
- ``block_size`` of the cipher. It is critical to
- never reuse a ``nonce`` with a given ``key``. Unlike
- :class:`~cryptography.primitives.block.modes.CBC`,
- reusing a nonce compromises the security of all data
- encrypted under the key.
+ :param bytes nonce: Recommended to be random. It is critical to never reuse
+ a ```nonce``` (or its subsequent incremented values)
+ with a given key. Any reuse of the nonce with the same
+ key compromises the security of every message encrypted
+ with that key. Must be the same number of bytes as the
+ ```block_size``` of the cipher with a given key. The
+ nonce does not need to be kept secret and may be
+ included alongside the ciphertext.
.. class:: cryptography.primitives.block.modes.OFB(initialization_vector)