How you can prove something existed — without showing it to anyone
1. Everything has a fingerprint
When you type text or pick a file on KnownSince, your browser computes its fingerprint — 64 characters that are unique to your exact content. (The technical name is a SHA-256 hash.) Three things make fingerprints special:
- The same content always gives the same fingerprint.
- The fingerprint reveals nothing about the content — it can't be reversed or "decoded."
- No one can craft a different document with the same fingerprint.
So if a fingerprint provably existed on some date, the content behind it must have existed too — and only whoever holds that content can demonstrate the match.
2. Bitcoin is a clock nobody controls
Roughly every ten minutes, the Bitcoin network adds a "block" to a public record kept by thousands of computers around the world. Each block has a time, and rewriting old blocks is practically impossible — that's the property that makes Bitcoin work as money, and it's the only part of Bitcoin we use. You don't need a wallet, an account, or any cryptocurrency. For us, Bitcoin is simply the world's most tamper-proof clock.
3. Your fingerprint gets written into that clock
We use an open standard called
OpenTimestamps: fingerprints from many
people are bundled together and anchored into the Bitcoin record. Your
receipt (a small .ots file) is the trail from your fingerprint
to that anchor. Once the anchor is in — usually within a few hours — your proof is permanent.
Why you don't have to trust us
- Your content is fingerprinted on your device and never uploaded.
- Your receipt can be checked against Bitcoin with free, independent, open-source tools — with our servers switched off, your proof still works.
- We couldn't backdate a proof if we wanted to: block times are set by the Bitcoin network, not by us.
What a timestamp does — and doesn't — prove
It proves your content existed no later than a moment in time. That's powerful evidence for "I had this first": an idea, a manuscript, a design, a prediction, a record. It is not, by itself, a patent, a trademark, or a copyright registration — for those you still need the official routes.
One important tip: keep the original
Your proof is about the exact content you stamped. Keep the original file unchanged — a re-saved photo or re-exported document gets a different fingerprint — and keep your receipt file with it.