Microsoft announces that PlayReady will support CBC encryption

Just in time for IBC, Microsoft announced that PlayReady 4.0 will support the CMAF interoperable format with AES-CBC encryption starting this month. It also plans to roll-out on Windows machines starting with Xbox before the 2017 holidays, followed by Windows 10 PCs in 2018.

As a reminder, Common Encryption has been adopted as a standardized method for content protection. It enables an encrypted file-set and its key to be used across multiple DRM systems, offering content providers the possibility to encrypt and package their content once per container/codec and use it with a variety of key systems and browser content decryption modules: Widevine for Chrome and Firefox, PlayReady for Microsoft and FairPlay for Apple.

While CENC has been a big step towards harmonizing the fragmented DRM market, historically these DRM technologies have supported two separate and incompatible encryption modes. Apple’s FairPlay supports cipher block chaining (CBC), while PlayReady, Widevine, and other DRMs supported counter mode (CTR).

Google and Adobe already made the switch to CBC last year and this formal announcement from Microsoft means that now all major DRMs will support CBC encryption.

This provides one of the final missing pieces of the Common Media Application Format puzzle. CMAF, which is designed allow broadcasters to deliver both HLS and DASH from a single set of source files, promises to lower the cost and simplify the complexity of serving multiple media formats. However, for premium content providers requiring DRMs, its utility was hitherto limited due to the need to encrypt files two different ways to reach all devices.

Of course complete adoption is still a way off, but when all devices catch up to CBC, broadcasters will need just one encrypted stream for every screen. No more duplicate formats, no more duplicate CDN cost. Ah interoperability…

1 thought on “Microsoft announces that PlayReady will support CBC encryption”

  1. As per CENC specification, both CTR & CBC modes should be implemented by the DRM and Playready 3.0 already provides the APIs for CbcEncryptData & CbcDecryptData. Then, what does it mean by CBC support in Playready 4.0? (Actually speaking, I haven’t ever seen CENC streams with CBC encryption.)

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