Consider our friendly, neighborhood PSSH box.

The semantics are simple — to identify encryption keys — but, as with any permissive specification, there’s a lot more going on than meets the eye. In some cases, they contain deeply nested little-endian UTF16 XML. In others, we’ll find protocol buffers containing base64-encoded JSON. In all cases, they have surprising amount of personality. In this talk, we will dive deep into several PSSH boxes, dissecting them bit by bit across various popular DRM schemes. Along the way, we will: 1. Explore the history of the PSSH box and how it mirrors the evolution of DRM standards. 2. Discover how each provider has imparted their own company idioms onto the loosely-defined PSSH payload. 3. Identify where the decisions of one provider impacted the rest. This talk was presented at Demuxed 2024, a conference by and for engineers working in video. Every year we host a conference with lots of great new talks like this in San Francisco. Learn more at https://demuxed.com