Citizen-captured photos and videos are becoming powerful reporting tools. But faked footage, or footage with missing crucial context, threatens to break the trust between a newsroom and its audience. Professional journalists thus need to be able to vet the footage captured by citizens to ensure that the files sent in by citizen journalists are authentic and accurate representations of the depicted event.

ProofMode (developed by the Guardian Project) promotes trust by providing a means to strongly authenticate multimedia at the point of capture.

We were the first to experiment with its distribution as a software library, under the name libProofMode. Starling Lab developed a bespoke fork of Signal Messenger that embeds authentication as a native feature. Users of this custom app can snap photographs directly within the app, which automatically generates a unique OpenPGP key pair to sign the media and its surrounding sensor metadata, including location, time, and cell tower environment.

At capture, media hashes are automatically registered on OpenTimestamps to create a “proof of existence” on the Bitcoin ledger. To ensure secure transport, every file sent via Signal triggers an automated MobileCoin micro-transaction; the first 16 digits of the “proof hash” are embedded in the transaction memo, allowing the recipient to cryptographically verify that the file received exactly matches the file captured in the field.

To reduce the burden on legal and journalistic investigators, the prototype features a visual layer of UI inside the Signal conversation view. Both sender and recipient can instantly surface contextual metadata snapshots and check them against immutable third-party record holders, such as the LikeCoin or Avalanche blockchains. This “glass-to-glass” approach ensures that technical authenticity markers are accessible and legible to the field practitioners who need them most.