Document the default key storage directory for macOS & Linux (#17674)

Author: scottaddie

aspnetcore/security/data-protection/implementation/key-storage-format.md

@@ -3,14 +3,17 @@ title: Key storage format in ASP.NET Core
 author: rick-anderson
 description: Learn implementation details of the ASP.NET Core Data Protection key storage format.
 ms.author: riande
-ms.date: 10/14/2016
+ms.date: 04/08/2020
 uid: security/data-protection/implementation/key-storage-format
 ---
 # Key storage format in ASP.NET Core
 
 <a name="data-protection-implementation-key-storage-format"></a>
 
-Objects are stored at rest in XML representation. The default directory for key storage is %LOCALAPPDATA%\ASP.NET\DataProtection-Keys\.
+Objects are stored at rest in XML representation. The default directory for key storage is:
+
+* Windows: *%LOCALAPPDATA%\ASP.NET\DataProtection-Keys\*
+* macOS / Linux: *$HOME/.aspnet/DataProtection-Keys*
 
 ## The \<key> element