Systems and methods for encrypting a media file for streaming and/or downloading over a network are disclosed. These systems and methods may be part of a larger media servicing network that can be used to, among other things, process uploaded media content, provide it for streaming, and collect metric information regarding the streaming. The disclosed systems and methods provide for receiving requests for a media file or a chunk of a media file and responding to these requests by encrypting the requested chunks dynamically and providing the chunks to the requesting entity. These systems and methods, which can be utilized with a dynamic chunk generation and dynamic index file generation, enable a high degree of flexibility in streaming chunked media files and preclude the need to encrypt the chunks prior to streaming. The systems and methods may also be applied to encrypting files for continuous streaming protocols as well as for progressive download.