We do not have a solution for putting a decryption key into MP4 files. We support integration with third party DRM providers.
Some DRM systems require a module in Wowza in order to function, for example [BuyDRM](http://How to set up and test BuyDRM KeyOS DRM %28PlayReady%29 ), EZDRM, Verimatrix. Others such as Widevine and PlayReady contact a license server and don’t require a Wowza module. More details on the various DRM offerings can be found here and here.
1) The MP4 file is not downloadable as Wowza Streaming Engine is a streaming server and not a web server. Content is encrypted during the streaming process.
2) The player requesting the content must support DRM for decoding the content. For example, with the Verimatrix DRM solution the DRM module, Wowza Streaming Engine, and the DRM client must all work together to allow playback on the DRM client.
3) Regardless of the DRM type used, only clients that can decode it’s content and have the correct decryption key and/or keys can play it back.
Please take a look at our documentation on DRM. It may help to clarify my response.