Merge pull request #29730 from bdewater/update-encryptor-docs

Update MessageEncryptor example to use dynamic key length

activesupport/lib/active_support/message_encryptor.rb

@@ -14,11 +14,12 @@ module ActiveSupport
   # This can be used in situations similar to the <tt>MessageVerifier</tt>, but
   # where you don't want users to be able to determine the value of the payload.
   #
-  #   salt  = SecureRandom.random_bytes(64)
-  #   key   = ActiveSupport::KeyGenerator.new('password').generate_key(salt, 32) # => "\x89\xE0\x156\xAC..."
-  #   crypt = ActiveSupport::MessageEncryptor.new(key)                           # => #<ActiveSupport::MessageEncryptor ...>
-  #   encrypted_data = crypt.encrypt_and_sign('my secret data')                  # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..."
-  #   crypt.decrypt_and_verify(encrypted_data)                                   # => "my secret data"
+  #   len   = ActiveSupport::MessageEncryptor.key_len
+  #   salt  = SecureRandom.random_bytes(len)
+  #   key   = ActiveSupport::KeyGenerator.new('password').generate_key(salt, len) # => "\x89\xE0\x156\xAC..."
+  #   crypt = ActiveSupport::MessageEncryptor.new(key)                            # => #<ActiveSupport::MessageEncryptor ...>
+  #   encrypted_data = crypt.encrypt_and_sign('my secret data')                   # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..."
+  #   crypt.decrypt_and_verify(encrypted_data)                                    # => "my secret data"
   class MessageEncryptor
     class << self
       attr_accessor :use_authenticated_message_encryption #:nodoc: