Verification

What is OpenTimestamps?

OpenTimestamps is an open standard for creating cryptographic timestamp proofs anchored to the Bitcoin blockchain. A .ots file contains a compact proof that a specific document existed before a certain Bitcoin block was mined — providing tamper-evident, independent evidence of prior art without relying on any central authority. Because Bitcoin's blockchain is globally distributed and immutable, these timestamps are verifiable by anyone, forever.

Download OTS Proof File

The single .ots file covers all 17 documents in this archive:

How to Verify (3 Steps — No Bitcoin Node Required)

1. Go to opentimestamps.org in your browser. No installation or account needed — the site works entirely in your browser.
2. Drag & drop the PDF you want to verify onto the verification area, then also drag the .ots file (downloaded above) onto the same area. The tool will compute the SHA-256 of your PDF and check it against the timestamp proof.
3. Read the result. A successful verification will display the Bitcoin block number and timestamp confirming the document existed before that block was mined. Cross-check the SHA-256 shown against the table below to confirm document integrity.

SHA-256 Hashes — All 17 Documents

Compare these hashes against your downloaded PDFs: sha256sum <file>.pdf (Linux/Mac) or Get-FileHash <file>.pdf -Algorithm SHA256 (Windows PowerShell).

hashes.txt (raw) — Zenodo Archive