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Corner

How it works

Stake a file in five steps. Verify the receipt forever.

  1. 01

    You upload a file.

    A draft, a sketch, a paper, a CAD file, a notebook page, a piece of source code — anything you want to claim priority on. Up to 50 MB at v1. The bytes you upload are exactly what gets witnessed.

  2. 02

    The registry hashes the file.

    SHA-256 over the bytes. The output is a 64-character fingerprint — a number that uniquely identifies your file. Change one byte, the fingerprint changes entirely. The registry stores the fingerprint; the file content is never sent anywhere except the storage you authorized.

  3. 03

    Multiple Time Stamp Authorities witness the fingerprint.

    The fingerprint is sent to several independent Time Stamp Authorities (TSAs) — public services run by certificate authorities like FreeTSA, DigiCert, Sectigo, GlobalSign. Each TSA signs the fingerprint with its private key against an atomic-clock-traceable timestamp. This is RFC 3161 — a 2001 standard with decades of legal precedent ([eIDAS][eIDAS] in the EU, [ESIGN][ESIGN] in the US).

    [eIDAS]: regulation EU/910/2014 · [ESIGN]: 15 USC 7001

  4. 04

    You get a receipt page.

    A public URL with the file fingerprint, the timestamp from each witness, downloadable proof tokens (one .tsr file per witness), and the exact openssl ts -verify command anyone can run. The receipt is yours. You can share the URL, embed it in a patent disclosure, cite it in a journal, or hand it to a court.

  5. 05

    Anyone can verify offline, forever.

    Download the original file, the witness .tsr token, and the witnessing TSA's public CA certificate. Run:

    openssl ts -verify \
  -data <your-file> \
  -in <witness>.tsr \
  -CAfile <tsa-cacert>.pem

    Successful output: Verification: OK. Corner doesn't need to exist for the proof to hold. The TSAs publish their certificates; trust stores in every operating system already include the major CAs.

Why multiple witnesses

One TSA witnessing your fingerprint is sufficient for most legal uses. Several independent TSAs witnessing the same fingerprint is structurally stronger: if any single TSA goes down, gets compromised, or has its certificate revoked years from now, the others still verify. Geographic + organizational diversity also makes the receipt resistant to single-jurisdiction legal pressure.

Privacy options

By default, the file you upload is published on the receipt page so anyone can verify the proof against the same bytes you witnessed. You can opt to keep the file private — the receipt then shows only the fingerprint, and you keep the file locally. The proof still verifies; you just have to produce the file yourself when verifying.

Stake your first file