add padding info to docs
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 2233d52..8316569 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -169,6 +169,8 @@
CBC (Cipher block chaining) is a mode of operation for block ciphers. It is
considered cryptographically strong.
+ **Padding is required when using this mode.**
+
:param bytes initialization_vector: Must be random bytes. They do not need
to be kept secret (they can be included
in a transmitted message). Must be the
@@ -211,6 +213,8 @@
cryptographically strong. It transforms a block cipher into a stream
cipher.
+ **This mode does not require padding.**
+
:param bytes nonce: Should be random bytes. It is critical to never reuse a
``nonce`` with a given key. Any reuse of a nonce
with the same key compromises the security of every
@@ -224,6 +228,8 @@
OFB (Output Feedback) is a mode of operation for block ciphers. It
transforms a block cipher into a stream cipher.
+ **This mode does not require padding.**
+
:param bytes initialization_vector: Must be random bytes. They do not need
to be kept secret (they can be included
in a transmitted message). Must be the
@@ -237,6 +243,8 @@
CFB (Cipher Feedback) is a mode of operation for block ciphers. It
transforms a block cipher into a stream cipher.
+ **This mode does not require padding.**
+
:param bytes initialization_vector: Must be random bytes. They do not need
to be kept secret (they can be included
in a transmitted message). Must be the
@@ -261,6 +269,8 @@
Additional means of verifying integrity (like
:doc:`HMAC </hazmat/primitives/hmac>`) are not necessary.
+ **This mode does not require padding.**
+
:param bytes initialization_vector: Must be random bytes. They do not need
to be kept secret (they can be included
in a transmitted message). NIST
@@ -365,6 +375,8 @@
identical plaintext blocks will always result in identical ciphertext
blocks, and thus result in information leakage
+ **Padding is required when using this mode.**
+
Interfaces
----------
@@ -377,8 +389,8 @@
finish the operation and obtain the remainder of the data.
Block ciphers require that plaintext or ciphertext always be a multiple of
- their block size, because of that **padding** is often required to make a
- message the correct size. ``CipherContext`` will not automatically apply
+ their block size, because of that **padding** is sometimes required to make
+ a message the correct size. ``CipherContext`` will not automatically apply
any padding; you'll need to add your own. For block ciphers the recommended
padding is :class:`cryptography.hazmat.primitives.padding.PKCS7`. If you
are using a stream cipher mode (such as