Encrypt the connection string

aspnet_regiis -pe ConnectionString  –app "/docs"

where –pe is the parameter used to encrypt the section. Connection string is the section, if you want to encrypt AppSettings, use appsettings instead of Connectionstrings. And the –app parameter is used to specify the application (it must be virtual path and need to start with “/”), if –app parameter is not specified it will encrypt the Root web.config. If the application is in File System, you need to specify –pef and Physical location as the parameter.

aspnet_regiis -pef ConnectionString  –app "D:\MyWebApp"

Decrypt the connection string

It is almost same as Encryption, only difference is instead of –pe use –pd. And in the case of –pef use –pdf.

aspnet_regiis -pd ConnectionString  –app "/docs"

and

aspnet_regiis -pdf ConnectionString  –app "D:\MyWebApp"

You can also specify the Provider for Encryption too. Use –prov parameter for providing custom provider (You can create your own provider, for this you need to inherit from ProtectedConfigurationProvider class). By default it will be RsaProtectedConfigurationProvider.
Screenshots – Before and After encrypting the app settings.

Before Encryption

After Encryption