Drop a file in, set a passphrase, and walk away with a sealed .vault container. The locking happens inside this browser tab using its own cryptography engine. Nothing is sent anywhere, so you could pull the network cable and it would still work.
Turns any file into an encrypted .vault. Your original stays untouched.
Opens a container made here (or by the offline script below) and gives back the original file, name included.
The container is a small header followed by AES-GCM sealed chunks. Everything needed to open it, apart from your passphrase, travels inside the file. You never depend on this website: the script underneath opens one with stock Node.js.
| Offset · size | Contents |
|---|---|
| 0 · 8 | magic "VAULTBX" then version byte 0x01 |
| 8 · 1 | key-derivation id, 1 = PBKDF2-HMAC-SHA256 |
| 9 · 4 | iteration count, uint32 big-endian (600,000) |
| 13 · 16 | random salt |
| 29 · 8 | random nonce prefix |
| 37 · 4 | plaintext bytes per chunk (4 MiB) |
| 41 · 4 | length of the sealed metadata |
| 45 · n | metadata: AES-256-GCM over JSON {name, type, size, mtime}, IV = prefix ‖ uint32(0). The file name is hidden as well. |
| then | chunk i (1…n): AES-256-GCM, IV = prefix ‖ uint32(i), each one chunk size + a 16-byte tag |
| AAD | the first 41 header bytes + one flag byte (2 = metadata, 1 = final chunk, 0 = any other). Altered parameters, shuffled chunks or a chopped-off ending all fail loudly. |
Straight answers to what people ask before trusting a locker with their files.
Nothing. Your browser reads the file, Web Crypto encrypts it, and the result comes back as a download. The page's security policy only permits contact with its own origin, and there is no upload route on the server at all. Load the page, go offline, and it keeps working.
The finished container is assembled in browser memory before download, and 200 MB is a comfortable ceiling for phones and older laptops. For anything larger, split it first or reach for a desktop tool such as age or VeraCrypt.
AES-256-GCM is a standard authenticated cipher, so a wrong passphrase or a single altered byte is caught. The real weak spot is the passphrase. 600,000 PBKDF2 rounds slow down guessing, yet a short or recycled passphrase can still be cracked offline by whoever holds the .vault.
We will never ask for them, and the safest home for them is offline, on paper or stamped metal, somewhere secure. If you do encrypt a backup, pick a long, unique passphrase and never keep it beside the file.
The contents, the original name, the type and the exact size (inside the metadata) are all encrypted. The .vault's own size is visible, so someone can estimate the original size to within a few bytes.
Yes. The format is versioned and documented above. Any .vault v1 file opens in Door B or with the offline script, today or years from now.