C2PA authentication for live streaming: proof of concept and MITM evaluation

What is it about?

This paper presents a proof-of-concept implementation of the C2PA (Coalition for Content Provenance and Authenticity) live streaming specification, demonstrating how cryptographic authentication can be embedded in real-time video streams to detect tampering and verify content provenance. The core technical challenge the authors address is that C2PA's existing video-on-demand authentication mechanism—which uses a Merkle tree hash covering an entire asset—is fundamentally incompatible with live streaming, where future segments do not yet exist when current segments must be signed. The paper implements the C2PA v2.3 "Verifiable Segment Information" approach, which uses short-lived session keys to cryptographically bind each media segment to a C2PA manifest carried in the stream's initialization segment, via DASH in-band event messages (emsg boxes) containing COSE_Sign1 signatures. A key result is that this session-key approach reduces bandwidth overhead to 0.56%, compared to approximately 5% for earlier per-segment manifest embedding—an 88.9% reduction—while achieving 100-millisecond average validation latency. The authors also construct a Man-in-the-Middle (MITM) evaluation framework using mitmproxy to test four attack scenarios: content replacement, alternate narrative construction through segment reordering, signature stripping, and manifest replacement with attacker-controlled certificates. The C2PA system successfully detected all four attack types. The paper concludes by identifying open standardization questions around session key management interfaces, certificate revocation latency, validation acceptance thresholds, and player library development—soliciting community feedback as C2PA live streaming specification work continues.

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Photo by Mark Farías on Unsplash

Photo by Mark Farías on Unsplash

Why is it important?

The proliferation of AI-assisted media manipulation has created an urgent need for scalable, real-time content authentication. Deepfakes, synthetic media, and selective editing can now be produced rapidly and at scale, eroding audience trust in video content—particularly news, sports, and other programming consumed live, where viewers have no opportunity to await third-party fact-checking before forming impressions. C2PA represents the broadcast and media industry's most serious standardized response to this threat, with backing from major camera manufacturers, social platforms, and news organizations. However, until this work, C2PA's practical applicability to live streaming remained unproven. Live content is arguably where authentication matters most—breaking news footage, live political events, and sports broadcasts are precisely the content most susceptible to interception, manipulation, and rebroadcast as something it is not. This paper's importance lies in demonstrating that the theoretical C2PA live streaming architecture is practically implementable with acceptable performance characteristics. The 0.56% bandwidth overhead is low enough to be commercially viable across CDN-delivered streaming at scale. The 100-millisecond validation latency is compatible with real-time playback workflows. The successful detection of all four MITM attack scenarios—including the subtle alternate-narrative attack through segment reordering—validates that the cryptographic design covers meaningful real-world threat vectors. By providing an open, reproducible proof-of-concept built on standard components—DASH, CMAF, mitmproxy, dash.js—the authors create a foundation that player developers, packager vendors, and standards bodies can build upon, accelerating the path from specification to deployed interoperable ecosystem.

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