"I called it" is easy to say afterwards. This proves it.
Write a prediction and seal it in your browser with SHA-256 and a random secret key. Publish the seal now: a post, an email, a group chat. When the outcome is known, reveal the receipt, and anyone can check that the text is exactly what you sealed.
Use it: kvantix.tech/playground/lock-your-prediction, or open index.html from this repository. It is one file, works offline, and its own security policy blocks every network request.
seal = SHA-256( "kvantix-seal-v1\n" + key + "\n" + text )
Four independent ways, all tested against the same test vectors on every commit:
| Command | |
|---|---|
| Any terminal | printf 'kvantix-seal-v1\n%s\n%s' "$KEY" "$TEXT" | sha256sum |
| Python 3.9+ | python3 verify.py check receipt.txt --seal <published seal> |
| Node 18+ | node verify.mjs check receipt.txt --seal <published seal> |
| Browser | index.html, panel 2 |
Always compare with the seal that was published, copied from the original post, not with the one written inside the receipt.
Seal from the command line (the receipt is written to a file and the seal is printed):
python3 verify.py seal "Denmark beats Norway 2-1 on 12 October." --reveal 2026-10-12| File | What it is |
|---|---|
SPEC.md |
The seal, text normalisation, receipt format and parsing rules. Stable: a change would be kvantix-seal-v2. |
test-vectors.json |
13 cases covering line breaks, Unicode NFC, what is and isn't trimmed, Danish letters and emoji. |
verify.py, verify.mjs |
Standalone verifiers and sealers. Standard library only, written separately so they check each other. |
seal-core.js, src/app.js, index.html |
The standalone page. index.html is built by tools/build_page.py, and CI fails if it doesn't match the sources. |
site/kvx-seal.js |
The exact script served on kvantix.tech, with its SHA-256. CI runs it against the test vectors, and a daily job compares it byte for byte with the live file. |
A seal proves what was written. It does not prove when: that comes from where and when the seal was published. Your device's clock proves nothing.
It also doesn't prove that this was your only prediction. Someone who seals ten guesses and reveals the one that came true has proven nothing. A track record only counts if every sealed call is published, misses included.
That rule is the core of how Kvantix validates trading signals and forecasts. The same idea runs in public in our weather forecast test.
The tool sends nothing and stores nothing: the text, the key and the seal stay in your browser, and Kvantix never sees them. The standalone index.html has no analytics and can't make network requests at all. The kvantix.tech page runs the same script, and the site counts page views with cookieless Umami. If you lose the receipt, nobody can recover it, including us.
MIT. © 2026 Kvantix (CVR 46296036), Hjørring, Denmark · validation@kvantix.tech