Open source · Self-hosted · Free
An open, self-hosted alternative to paid AATL certificate seals. Prove a document is authentic and unaltered with your own certificate authority, and anchor the proof to a decentralised public ledger so anyone can verify it — independently, and for free.
No per-seal or per-envelope fees. The cryptography behind a document seal is free and standard — there's no reason to rent it.
Seal documents with your own certificate authority. Tamper-evident PAdES signatures, entirely under your control — trust flows from your own published root.
Every seal gets an independent, decentralised timestamp via OpenTimestamps — free, permanent proof of when a document existed, recorded on a public ledger no one controls.
Anyone can confirm a document on the public portal, or offline with stock tools — the proof carries everything a verifier needs. Independently checkable, anywhere.
We believe proof of authenticity should be public infrastructure — not a subscription.
Proving a document is real shouldn't mean paying to join a private trust list. The tools to prove a document is genuine should belong to everyone — not sit behind a certificate vendor's paywall.
A cryptographic seal proves who and what. An independent timestamp proves when. Together, anyone can verify both. Let's Seal holds no cryptocurrency and you never touch a coin or a wallet — we use the public ledger the way a notary uses a public register: to stamp a record no one can alter.
Your own certificate authority signs the finished PDF (PAdES). Tamper-evident, standards-based, and entirely yours.
The document's SHA-256 gets an independent, decentralised timestamp via OpenTimestamps — free, permanent proof of existence and date, on a public ledger no one controls.
A public proof page — plus a QR on every sealed page — lets anyone confirm authenticity, independently and offline.
Paid AATL seals add one thing the free, standard cryptography doesn't: an automatic trust indicator inside Adobe Reader. Here is the full picture.
Every sealed document has a public proof page and a downloadable OpenTimestamps proof you can check against the blockchain yourself. The proof stands on its own, forever.
Free, open source, and self-hostable. No account needed to verify.