emarsden / pssh-box-wasm

Parsing and printing PSSH boxes for DRM systems, in WebAssembly.

pssh-box-wasm

A collection of web-based tools for working with PSSH boxes (as used for the initialization of DRM systems) and with Widevine Content Decryption Modules (CDMs). There are tools that allow you to:

• serialize and deserialize (create and decode) PSSH boxes
• request decryption keys (obtain a license) from a Widevine DRM licensing server
• convert Widevine CDMs between blob format and “WVD” format

The tools use code from the Rust crate pssh-box compiled to WebAssembly (WASM), and run fully in your web browser (there is no server backend; the tools will work fully offline once loaded).

Tip

You can try out the tools in your browser.

PSSH boxes are used:

• in an MP4 box of type pssh in an MP4 fragment (CMAF/MP4/ISOBMFF containers)

• in a <cenc:pssh> element in a DASH MPD manifest

• in an EXT-X-SESSION-KEY field of an m3u8 playlist

A PSSH box includes information for a single DRM system. This library supports the PSSH data formats for the following DRM systems:

• Widevine, owned by Google, widely used for DASH streaming
• PlayReady, owned by Microsoft, widely used for DASH streaming
• WisePlay, owned by Huawei
• Irdeto
• Marlin
• Nagra
• The unofficial variant of Apple FairPlay that is used for DASH-like streaming by Netflix
• Common Encryption

PSSH boxes contain (depending on the DRM system) information on the key_ID for which to obtain a content key, the encryption scheme used (e.g. cenc, cbc1, cens or cbcs), the URL of the licence server, and checksum data.

Useful references:

• Information from the W3C on the cenc initialization data format

• Widevine diagnostics tools

• The Shaka packager utility includes a Python script pssh-box.py which is able to decode and create Widevine initialization data.

License

This project is licensed under the MIT license. For more information, see the LICENSE file.