documentation improvements for KDF
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 14ca688..975a7b0 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -136,6 +136,8 @@
.. class:: PBKDF2Backend
+ .. versionadded:: 0.2
+
A backend with methods for using PBKDF2.
.. method:: pbkdf2_hash_supported(algorithm)
@@ -157,7 +159,7 @@
provider.
:param int length: The desired length of the derived key. Maximum is
- 2\ :sup:`31` - 1.
+ 2\ :sup:`31` - 1.
:param bytes salt: A salt.