To encrypt an ASP.NET application’s connection strings?by the path of the application, navigate to the .NET framework folder ?%windows%\Microsoft.NET\Framework\versionNumber
Open the command prompt as administrator and point to the .Net directory and run the command
ASPNET_REGIIS -pef “connectionStrings” “C:\Inetpub\<Application Folder>”
(Point to the directory not the web.config file)
If successful the following should be displayed.