Recommend that recipes include a version
diff --git a/docs/contributing.rst b/docs/contributing.rst
index cb9c728..cec067c 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -77,6 +77,10 @@
if not is_valid:
raise InvalidSignature
+Every recipe should include a version or algorithmic marker of some sort in its
+output in order to allow transparent upgrading of the algorithms in use, as
+the algorithms or parameters needed to achieve a given security margin evolve.
+
APIs at the :doc:`/hazmat/primitives/index` layer should always take an
explicit backend, APIs at the recipes layer should automatically use the
:func:`~cryptography.hazmat.backends.default_backend`, but optionally allow