Sealed Message
Lock a message with a passphrase. Only someone with the same passphrase can open it.
Only matters when sealing. Opening detects the style.
How this works
- Everything happens inside this page on your device. The page is blocked from using the network, so nothing you type can be sent anywhere.
- Your passphrase is stretched into a key with PBKDF2 (600,000 rounds of SHA-256), and the message is locked with AES-256-GCM. Both come from your browser's built-in encryption.
- The sealed text includes a tamper check. If any part is changed or missing, it will refuse to open.
- A wrong passphrase and a damaged message look the same to the page. It cannot tell you which one happened.
- Agree on the passphrase in person or on a call, never in the same chat as the sealed text. Four or more random words make a strong one.
- Nothing is saved. Closing or clearing the page removes everything.