How encryption for Cinema Movies works

Summary

The Cinema Industry is using its own standards for creating and distributing movies in a secure way. The DCI (Digital Cinema Initiatives) specification defines everything from file formats and encryption to the projection systems itself. The specification itself is publicly available but relies on various IEEE (Institute of Electrical and Electronics Engineers) and SMPTE (Society of Motion Picture and Television Engineers) standards, which have to be purchased. Scope This document will show a rough overview of the DCI workflow and describe in detail how the encryption of a DCI movie works. It will not show how to break any encryption and no encryption has been broken while writing this document. From our perspective, the DCI standard is safe. The author of this document has been operating a cinema since 2021, without any insight to the distribution or production side of the industry. Some information may be incomplete. How it’s started End of 2023 the movie WONKA was released. Some cinemas reported, that they are unable to start this movie on their projector. The reason was, that a certificate used by the distributor was expired. This certificate was used to sign the DCP files. The distributor published new files, starting the movie worked again. Out of curiosity the author started to check how the validation process on the projector is working. Glossar DCP: Digital Cinema Package - A folder which contains all components of a movie. Metadata, Subtitles, Audio and Picture in seperate files CPL: Composition Playlist - A DCP can contain multiple audio and video streams which will combined in a CPL KDM: Key Delivery Message - A XML file which contains the cryptographical information to allow a movie playback on a specific DCI certified projection system DKDM: Distribution Key Delivery Message - Similar to a KDM, but for a remastering or distribution system, not for a projection system Distribution Process graph TD classDef red fill:#a91900 classDef green fill:#126500 cl...