This article explains DRM fundamentals, the FairPlay workflow, key management methods using AVAssetResourceLoader and AVContentKeySession, tips for handling codec tags, and step‑by‑step guidance for downloading HLS videos with AVAssetDownloadTask and AVAggregateAssetDownloadTask on iOS.
The article explains iOS FairPlay DRM implementation, detailing the encryption workflow, SPC/CKC exchange, and key terminology, and compares two key‑management methods—AVAssetResourceLoader and the newer AVContentKeySession—while covering usage scenarios such as on‑demand, pre‑warming, offline playback, persistable keys, and video downloading via AVAssetDownloadTask.
The article dissects Apple’s FairPlay DRM, detailing its kernel‑driver and daemon decryption workflow, the LC_ENCRYPTION_INFO metadata, per‑user licensing files, LLVM‑level obfuscation techniques such as opaque predicates and control‑flow flattening, and the identified weaknesses that enable reverse‑engineering and key extraction.
