ISO/IEC 23001-7:2023

Overview

ISO/IEC 23001-7:2023 defines Common Encryption for files based on the ISO base media file format (ISO/IEC 14496-12). It specifies metadata formats, encryption schemes and processing rules that allow the same media file or stream to be consumed by multiple Digital Rights Management (DRM) and key management systems. The standard uses AES-128 symmetric encryption and supports both AES-CTR and AES-CBC protection schemes, plus subsample and pattern-based selective encryption for efficient video processing. An XML representation (for example, for DASH MPD use) is also defined to enable interoperable license and key management prior to download.

Key topics and technical requirements

• Encryption algorithms: AES-128 symmetric block cipher; modes specified include AES-CTR and AES-CBC.
• Protection scheme types: Scheme identifiers such as cenc, cbc1, cens, cbcs, and sve1 are defined for different use cases (full, pattern, subsample, and codec-sensitive encryption).
• Metadata boxes: Definitions and semantics for ISO BMFF boxes like TrackEncryptionBox, SampleEncryptionBox, ProtectionSystemSpecificHeaderBox, ItemEncryptionBox, and ItemAuxiliaryInformationBox.
• Key and IV handling: Identification of encryption keys using Key IDs (KIDs), initialization vector (IV) storage and processing rules; support for multiple keys and IVs per protected sample (added in the 2023 edition).
• Subsample encryption: Support for NAL-structured video (AVC/HEVC) to allow normal processing/editing of bitstreams prior to decryption.
• Pattern encryption: Partial encryption using repeatable patterns of encrypted and clear blocks to reduce device CPU load while protecting essential content.
• XML mapping: XML attributes/elements such as cenc:default_KID and cenc:pssh for inclusion in DASH ContentProtection descriptors and other XML delivery mechanisms.

Practical applications and who uses it

ISO/IEC 23001-7 is essential for:

• Content providers and OTT platforms packaging encrypted media for multi-DRM delivery.
• DRM vendors and key management systems that need interoperable metadata for key lookup and license delivery.
• Media packagers and encoders integrating sample-level encryption (full, subsample, or pattern) into ISOBMFF files.
• Device and player manufacturers implementing decryption pipelines and ensuring compatibility with multiple DRM systems.
• Streaming service integrators using DASH (MPD) with cenc metadata for pre-play license negotiation.

Benefits include easier cross-DRM interoperability, reduced duplication of encrypted assets, and optimized playback performance for constrained devices.

Related standards

• ISO/IEC 14496-12 - ISO Base Media File Format (base for this specification)
• MPEG DASH MPD delivery (XML descriptors like ContentProtection are referenced)
• Other parts of the ISO/IEC 23001 series (MPEG systems technologies)

Keywords: common encryption, ISO base media file format, AES-128, AES-CTR, AES-CBC, subsample encryption, pattern encryption, DRM, KID, cenc, cbcs, cbc1, cens, sve1, DASH, MPD.