Use SHA-1 for non-sensitive digests by default

Instead of providing a configuration option to set the hash function,
switch to SHA-1 for new apps and allow upgrading apps to opt in later
via `new_framework_defaults_5_2.rb`.

2 files changed, 5 insertions, 3 deletions

diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 780e69c146..cd9f4b4a68 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -100,9 +100,9 @@ called key-based expiration.
 
 Cache fragments will also be expired when the view fragment changes (e.g., the
 HTML in the view changes). The string of characters at the end of the key is a
-template tree digest. It is an MD5 hash computed based on the contents of the
-view fragment you are caching. If you change the view fragment, the MD5 hash
-will change, expiring the existing file.
+template tree digest. It is a hash digest computed based on the contents of the
+view fragment you are caching. If you change the view fragment, the digest will
+change, expiring the existing file.
 
 TIP: Cache stores like Memcached will automatically delete old cache files.
 
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 1668f9e81a..879a1ea89f 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -672,6 +672,8 @@ There are a few configuration options available in Active Support:
 
 * `config.active_support.time_precision` sets the precision of JSON encoded time values. Defaults to `3`.
 
+* `config.active_support.use_sha1_digests` specifies whether to use SHA-1 instead of MD5 to generate non-sensitive digests, such as the ETag header. Defaults to false.
+
 * `ActiveSupport::Logger.silencer` is set to `false` to disable the ability to silence logging in a block. The default is `true`.
 
 * `ActiveSupport::Cache::Store.logger` specifies the logger to use within cache store operations.