YouSaidThat: A cryptographic tool to timestamp and seal predictions with blockchain verification
By
Giulio Parrinello
Summary
YouSaidThat is a cryptographic tool that lets users seal predictions or statements with encryption, timelock, and blockchain anchoring. Users write a prediction that gets encrypted in-browser (AES-256-GCM), the decryption key is timelock-sealed using drand (so it doesn't exist until a chosen date), and a SHA-256 hash is anchored on Bitcoin via OpenTimestamps plus RFC 3161 timestamping. When revealed, anyone can cryptographically verify the exact content and timestamp without trusting any platform. No accounts needed, fully auditable, and built on open cryptographic standards.
Source
Product HuntYouSaidThat: A cryptographic tool to timestamp and seal predictions with blockchain verificationproducthunt.comKey quotes
· 5 pulledI built YouSaidThat because 'I called it first' is impossible to prove after the fact.
Screenshots get edited, timestamps can be faked.
You write a prediction, it's encrypted in your browser (the server never sees your text), and the decryption key is timelock-sealed with drand: it Literally doesn't exist until the date you pick.
When you reveal, anyone can verify you wrote exactly that.
No accounts needed. Fully auditable. Your proof lives outside any server.
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