Overview
ISO 26430-1:2008 specifies the Digital Cinema (D‑cinema) Key Delivery Message (KDM) - an XML‑based, secure message format used to transport content decryption keys and usage rights between D‑cinema content processing centers (for example, post‑production → distribution → exhibition). The KDM carries three fundamental information types: content keys for a specified Composition Play List (CPL), content key parameters (primarily the valid key usage date/time window), and the Trusted Device List (TDL) identifying equipment authorized to use the keys.
Key topics and technical requirements
- Message structure: KDM is an instance of the D‑Cinema Extra‑Theatre Message (ETM) XML wrapper and includes specific child elements (e.g., KDMRequiredExtensions, AuthenticatedPrivate).
- Content key transport: Content keys are listed (KeyId) in plaintext within RequiredExtensions while actual key values are carried encrypted in individual EncryptedKey elements so recipients can selectively decrypt keys.
- Usage windows: Each content key includes validity timestamps (ContentKeysNotValidBefore / ContentKeysNotValidAfter) defining permitted playback windows.
- Trusted Device List (TDL): Identifies devices (by certificate/identifier) allowed to decrypt and use the content keys.
- Security primitives: Uses XML Encryption and XML Signature primitives, with X.509 digital certificates for authentication. KDMs typically encrypt individual keys with RSA (allowing hardware security modules to process keys) and reference standards such as AES, SHA, and OAEP where applicable.
- Signature & authenticity: A Signature element carries the signer’s certificate chain and protects the integrity of authenticated sections.
- Interoperability focus: Designed to operate with constrained secure hardware (Secure Processing Blocks) and without requiring recipients to store multiple root certificates.
Note: the standard notes potential patent claims related to some elements; implementers should verify licensing where applicable.
Practical applications and users
- Who uses ISO 26430-1: film studios, post‑production houses, digital content distributors, theatrical exhibitors, theater management system (TMS) vendors, security managers, and system integrators.
- Typical uses:
- Issuing KDMs from distribution to cinema servers to enable scheduled screenings.
- Conveying time‑limited playback rights for pre-release screenings or limited engagements.
- Managing authorized device lists for secure playback across exhibition hardware.
- Benefits: standardized, interoperable key delivery; secure, auditable transfer of playback rights; compatibility with hardware security modules and existing D‑cinema certificate infrastructures.
Related standards
- SMPTE/ETM Generic Extra‑Theatre Message Format (referenced by ISO 26430‑1)
- ISO 26430‑2 (Digital certificate) and ISO 26430‑3 (Generic extra‑theatre message format)
- Relevant cryptographic and protocol references cited in the standard (X.509, XML Encryption/Signature, RFC3339 timestamps, UUIDs)
Keywords: ISO 26430-1:2008, KDM, digital cinema, D‑cinema, key delivery message, content keys, CPL, TDL, XML, X.509, RSA, encryption.
