Verifying the data

This site tells you what a wine cost on a given day, and what kind of company stands behind the label. Normally you would have to take that on trust: any website can quietly change a number later, or soften what it said about a producer, and nobody would ever notice.

We have made that impossible for ourselves. Every night everything we have recorded is reduced to one short string of characters — a cryptographic fingerprint — which changes completely if even a single digit in a single record changes. That string is published outside this site, in a place we cannot reach afterwards. So if we were to change yesterday's price, or yesterday's verdict about a winery, the fingerprint would stop matching — and anyone could see it.

None of this is our own invention. The fingerprint is sealed into the Bitcoin blockchain through OpenTimestamps, an open standard that has been used for a decade to date documents, archives and research; the same underlying trick — a Merkle tree — is what lets your browser tell a genuine site from a fake one. The program that checks our fingerprints is not ours either: it is free software, and it reads ours exactly as it reads anyone else's.

What this gives you: when a page here says a price has fallen over six months, or that we downgraded a company in March, you can check it rather than believe it. And a winery that disagrees with its category is arguing with a dated decision, not with a database field we are free to edit while the argument is going on.

It proves one thing and no more: that we knew exactly this on exactly that day. It does not make the fact true — a price we recorded may have been wrong in the shop's own catalogue, and a classification may rest on incomplete sources. What is protected here is the history of our statements, not their correctness.