ISO 26430-1:2008 defines a “key delivery message” (KDM) for use in digital cinema systems. The KDM has been designed to deliver security parameters and usage rights between digital cinema content processing centres (e.g. from post production to distribution, or from distribution to exhibition). The KDM carries fundamentally three information types:

• content keys for a specified composition play list (CPL);
• content key parameters – primarily the permitted key usage date/time window;
• the trusted device list (TDL) which identifies equipment permitted to use the content keys.