Supporting a plurality of content protection systems in a single container file. The protection systems share an encryption method which is accessible from a sample encryption box in the file. Each of the protection systems stores, in a protection system header box, information for decrypting the content in accordance with the corresponding protection system. In some embodiments, separate protection system header boxes in the file correspond to each of the protection systems. By using the common encryption method and sharing encryption expressions across the protection systems, the multiple content protection systems are supported in the file without creating additional copies of the content. In some embodiments, aspects of the disclosure extend the International Organization for Standardization (ISO) base media file format to support multiple digital rights management (DRM) systems in the single container file.