diff --git a/INSTALL b/INSTALL
index 559a441dbd..ceb73c3b9c 100644
--- a/INSTALL
+++ b/INSTALL
@@ -17,11 +17,13 @@ hosting provider prior to installation.
 	- Apache with mod-rewrite enabled and "Options All" so you can use a 
 local .htaccess file
 
-	- PHP > 5.1. The later the better. You'll need 5.3 for full openssl 
+	- PHP > 5.1. The later the better. You'll need 5.3 for encryption of key
+exchange conversations
 encryption support
 		- PHP *command line* access with register_argc_argv set to true in the 
 php.ini file
 		- curl, gd, mysql, and openssl extensions
+		- mcrypt (optional; used for end-to-end message encryption)
 
 	- Mysql 5.x