Step 1 · Capture
Choose the file to receipt
A signed agreement video, a PDF, a scan — anything. It stays in your browser. Only its 32-byte SHA-256 digest is sent to the Bitcoin calendars; the file itself is never uploaded by this demo.
Step 2 · Hash
SHA-256 fingerprint
Computed locally with Web Crypto. If even one byte of the file changes, this fingerprint changes.
…
Step 3 · Payment
$3 — demo only
No card is collected and nothing is charged. Real payment rails (Stripe, Flutterwave) are Phase 3 and need founder-supplied keys.
Step 4 · Anchor
Anchor on Bitcoin
Submits the SHA-256 to public OpenTimestamps calendar servers. They return a pending proof immediately; Bitcoin confirmation follows in hours (sometimes up to ~a day).
Step 5 · Receipt
Your Agreement Receipt
What this proves.