Photo and file hash proof

Capture or upload a file and verify its SHA-256 fingerprint

Open ProofCam
File limit 20 MiB

Create file proof

Use the camera button for an image or phone camera; use the file button for an allowed general file. Paste an existing SHA-256 to verify prior proof.

Upload photo No file selected

Before choosing a file from Dropbox, iCloud Drive, OneDrive, or another cloud drive, make sure it has been downloaded to this device.

Leave blank to only output the SHA-256 calculated from this file.

Proof Camera API documentation

Four steps

How to create file proof

Start by capturing or selecting a file, create its digital fingerprint, complete security processing, and then choose the right preservation and publication method.

  1. Phone camera, photo, and general file upload illustration

    Capture or choose a file

    Use a phone camera for images, or select an allowed general file such as a PDF, Office document, archive, audio, or video.

  2. Server-side SHA-256 calculation and security scanning illustration

    Create and inspect the fingerprint

    The server calculates or compares SHA-256 and queues the file for security scanning. Only images receive additional EXIF and embedded C2PA analysis.

  3. Private storage, blockchain time anchor, and public IPFS preservation illustration

    Choose a preservation level

    The original is temporary for 24 hours by default. Keep it private on CashLink, write only its SHA-256 to BCH as a public time anchor, or publish the original to IPFS.

  4. Digital fingerprint comparison, secure download, and sharing-link illustration

    Verify, download, or share intentionally

    Recalculate the fingerprint to check whether the content still matches. Members download saved originals, and a public download page appears only after a sharing link is explicitly created.

Technology and evidence

Proof features explained

Time anchoring, digital fingerprints, provenance analysis, and decentralized storage solve different problems. Used together, they create a more complete evidence trail.

Digital fingerprint anchored to a public blockchain time marker illustration

Why create proof?

Dates stored inside digital files can be changed, so they cannot establish when a file was produced by themselves. Writing its SHA-256 to the public BCH chain creates an independently verifiable, tamper-evident time anchor showing that matching content existed no later than transaction confirmation. It does not prove the actual capture or creation time, or that the content is true.

A file change producing a different SHA-256 fingerprint illustration

SHA-256 digital fingerprint

The same file bytes produce the same fingerprint, while any content change will normally produce a completely different result. A hash is not encryption and does not determine whether a file is truthful by itself.

Image EXIF, C2PA credentials, and external AI advisory analysis illustration

AI and content credential tools

After an image passes security scanning, CashLink analyzes EXIF and embedded C2PA. You must reselect the file yourself for external AI tools; CashLink never sends it automatically, and their results are advisory only.

Content distributed by CID across multiple IPFS nodes and repinned illustration

Decentralized storage: permissionless IPFS

IPFS addresses content by CID, and anyone with that CID can retrieve or repin the public original. A password or CashLink deletion cannot recall copies held by other nodes, while continued availability still depends on nodes keeping the content pinned.

Interactive evidence lab

Assemble your digital evidence trail

Help the camera companion complete three missions and see what private preservation, public sharing, content addressing, and an on-chain time anchor each add.

Front-end simulation only
Digital evidence trail adventure map A camera stands in the center with four paths leading to private CashLink storage, a public CashLink share, IPFS, and BCH. Private CashLink storage Private original vault CashLink public share Public website sharing page IPFS Public CID content address BCH Permanent public time anchor SHA-256 9f4a…c82d
  1. Private vault
  2. Public retrieval
  3. Time anchor

    This is a Legacy BCH address

    Legacy addresses can make the network and purpose harder to verify. We recommend converting it to CashAddr with the on-site tool. If you have verified the recipient, you may allow this submission once.

    Open BCH address converter