BA | Stamp for Gmail

Stamp a received email on Polygon + Bitcoin. The email never leaves your device: only its SHA-256 hash is sent.

BA | Stamp for Gmail timestamps an email you have open in Gmail — received or sent — by anchoring its cryptographic fingerprint on the Polygon and Bitcoin blockchains. The email is hashed in your browser with SHA-256; only that hash leaves your device. The message body, attachments and recipients are never transmitted. WHAT IT'S FOR • Prove an email existed, unchanged, at a specific moment. • Received email — keep the sender's DKIM/SPF/DMARC results as part of the proof. • Sent email — a self-stamp proving the content you authored existed at that time. • Evidence, disputes, IP and authorship: a verifiable record you can hand to anyone. HOW IT WORKS 1. Open an email in Gmail. A small BA | Stamp badge appears on the subject line. 2. Click it, review the email, then confirm (1 credit). The extension reads the raw message (.eml) in your browser, hashes it with SHA-256, and sends only that hash to the public bastamp.com API. 3. The hash is anchored on Polygon in the next batch (~5 minutes); a Bitcoin confirmation follows within ~24h via OpenTimestamps. 4. A proof packet is saved to your Downloads folder: the original .eml, the authentication results, a human-readable email.pdf, the server certificate, a proof.json for the open-source verifier, a README and a manifest. WHAT GETS SENT Only the SHA-256 hash of the raw email, the email's subject line (used as the stamp's file name so the certificate can name it), and the MIME type. THE EMAIL ITSELF NEVER LEAVES YOUR BROWSER — body, attachments and recipients are not transmitted, not stored, not analyzed. WHAT'S IN THE PROOF PACKET • original.eml — the exact bytes that were hashed (the timestamped object). • authentication.txt — for a received email, the DKIM/SPF/DMARC results recorded by the receiving server; for a sent email, a note that it is a self-stamp (no third-party authentication). • email.pdf — a human-readable rendering of the email, for reading and filing. It is NOT the timestamped object; the hash is of original.eml. • certificate.pdf — the server-issued certificate with the on-chain anchor. • proof.json — machine-readable proof for the open-source verifier. • README.txt and manifest.json — how to verify, and the SHA-256 of every file in the packet. HOW TO VERIFY A STAMP Visit bastamp.com/verify/<hash> (the extension shows the link) and check the packet against the public blockchain anchor. The open-source verifier at github.com/stamp-verify/stamp-verify confirms the on-chain match without any trust in bastamp.com. PRICING Each confirmed stamp uses one credit from your bastamp.com account. The first stamp on a new account is free; packs available at bastamp.com/pricing.