BlockFact

BlockFact introduces .facti — a new image file format that proves a photo is authentic, unedited, and captured at a verified time and place.

Every photo you take with BlockFact is cryptographically sealed at the moment of capture. The result is a .facti file—an image with built-in proof of origin that anyone can verify, without trusting the photographer, the platform, or us.

HOW IT WORKS

1. Take a photo with BlockFact
2. Your device generates a zero-knowledge proof and Poseidon hash—entirely on-device, no upload required.
3. The proof is registered on the StarkNet blockchain.
4. A .facti file is built locally on your phone—containing the image, an invisible watermark, and the on-chain registration.

The photo never leaves your device. Only a small cryptographic proof is sent to the blockchain.

WHAT MAKES .FACTI DIFFERENT

Unlike JPEG or PNG, a .facti file carries its own proof of authenticity:

• When was it taken? Verified by on-chain timestamp.
• Where was it taken? GPS coordinates sealed in the cryptographic hash
• Who took it? Linked to the creator's blockchain wallet
• Has it been edited? The invisible watermark and hash detect any tampering.

Anyone can verify a .facti file at blockfact.io/verify—just drag and drop.

WHO IS THIS FOR?

• Journalists documenting events where authenticity matters
• Photographers proving original work and protecting against AI-generated fakes
• Legal and insurance professionals who need verifiable visual evidence
• Content creators establishing provenance before publishing
• Anyone who needs to prove a photo is real

FOR DEVELOPERS

BlockFact is also available as a React Native SDK (@blockfact/react-native-facti-pro) for developers building apps that need verified image capture. The BlockFact app is the
reference implementation—try it to understand the .facti format, then integrate the SDK into your own product.

PRIVACY BY DESIGN

• Photos never leave your device—only a cryptographic hash is registered on-chain.
• No accounts required beyond sign-in—no personal data collected
• Zero-knowledge proofs mean the blockchain verifies your proof without seeing your photo.
• Open verification—anyone can check a .facti file independently

BUILT ON

• StarkNet blockchain (Ethereum L2)
• Groth16 zero-knowledge proofs via Arkworks
• Poseidon hashing (quantum-resistant)
• IANA-registered MIME type: image/vnd.blockfact.facti