SMPTE ST 430-3:2012

This standard presents a specification for a generic Extra-Theatre Message (ETM) format for use with unidirectional communications channels used in security communcations for Digital Cinema (D-Cinema) systems.

The ETM specification is a generic XML security wrapper that includes specific fields which can be extended to carry different kinds of information to meet various application-level requirements. (For example, the Key Delivery Message (KDM) is a specific instance of this format.) The ETM uses W3C Extensible Markup Language (see [XML]) to represent the information payload. It provides security using the XML encryption and signature primitives.