Tostis .nomedia Handler (com.tostis.nomediahandler) on Google Play
This app lets you hide multimedia content from standard Android apps.If you mark a folder as "hidden", it will not be shown in programs like gallery.In some cases is necessary to delete app cache from settings - apps - gallery, media storage or any other app.PS. Files can be read with a common file manager o with every app that does not process .nomedia files. Files are not hidden or encrypted but only marked as "hidden" to apps that manage .nomedia files in the right way.