For a reader holding a file
What is this file?
You bought something online, and your download included one or two extra
files ending in .attest or .private.attest. This page
explains what they are.
Each file is a small, signed receipt carrying the seller's claims about the listed transaction. The seller's signature lets anyone check those exact claims and detect later changes; it does not prove that the named person paid or participated. Keep it the way you'd keep an important paper receipt — it doesn't live in any account. It survives the shop closing. A seller's declaration that its signing key was compromised can invalidate receipts signed with that key. The standard provides a rescue for receipts with qualifying evidence that they were logged and anchored before the declaration. The command line can prepare and verify that evidence, with an external timestamp and separately configured trusted anchors. The bridge does not produce it automatically, and the verifier on this site currently pins no anchors.
You can check it yourself, without the store
You don't need to trust this page, or the store, or take anyone's word for it. Anyone can verify the receipt directly — including you, right now, in your browser, with the file never leaving your machine.
Never send *.private.attest to anyone.
That file carries the binding secrets for your receipts: anyone holding it can make the binding check report possession of those secrets. That result does not establish who bought anything.
Because one private file covers your whole library, handing it over lets its holder produce that same possession result for every receipt inside, not just the one you meant to show.
A real store or support agent will never need it — they can already see your order.
Keep it private, the way you would keep a paper receipt with your card number on it.
If anyone needs to see what you bought, send them the other file from your download instead — the one whose name ends in .attest but not in .private.attest. It shows the same purchases and gives no one a way to claim them.
What if the store is gone?
That's the whole point of this format: the receipt still works. It doesn't call home, it doesn't need the store's servers to be running, and it doesn't expire when a shop closes down. A verifier can check it entirely offline, months or years later, using nothing but the file itself and the seller's published signing key. If a store shuts down, the receipt still proves exactly what that store signed; it does not prove who made the purchase. It isn't the thing itself, but it's the part of your purchase that survives the store.
Never heard of any of this? Start here. Curious about the cryptography behind this? See the attest specification and the project on GitHub.