Saving the data for later play is one of the rights you manage with DRM - if you're not supposed to be able to play it later and the client allows you to, it's

Saving the data for later play is one of the rights you manage with DRM - if you're not supposed to be able to play it later and the client allows you to, it's ignoring the granted rights. Sharing the data with friends is another "right" in DRM. What you're describing is authentication - something that you can clearly do within HTML5 as is.