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Lockbox guide

Send a file securely without uploading it

Lock the file before it leaves your device, then send it any way you like. With Lockbox the file is locked in your browser, so no service ever holds a readable copy: email, chat apps and shared drives only carry the locked box.

Updated · 4 min read

Why lock it first

Email and chat apps protect messages on the way, but copies sit in inboxes, backups and devices, often for years. A file-sharing service holds the readable file on its servers. Locking the file first means every one of those copies is useless without the password.

How to do it

  1. Open Lockbox and add the files. Several go into one box.
  2. Set a password, or tap Make one for me.
  3. Tap Lock and Save.
  4. Send the file one way: email, WhatsApp, AirDrop, a shared drive or a USB stick.
  5. Send the password another way: a text, a phone call or in person.
The two-routes ruleIf the file and the password travel together, anyone who gets one gets both. Different routes mean someone would need to get into two places at once.

How the other person opens it

They go to yuzool.com/lockbox, choose Unlock, pick the file and type the password. It works in any modern browser on a phone or computer, with nothing to install, and unlocking is free whatever the size.

If they’d rather not visit a website, send a self-opening file instead: they open it in a browser and it unlocks itself, even with no internet.

For a short secret: a note in a link

For a Wi-Fi password, a door code or a few lines, choose Lock a note. The note is locked into a link, after the #, the part of an address that browsers never send to a server. The link opens a page that asks for the password. Notes can be up to 2,000 characters.

Questions

Is email secure enough for the locked file?

Yes. The box is locked with AES-256 before it’s sent, so whoever handles the email on the way sees only locked data. Keep the password out of that email.

Does the other person need Lockbox?

They need a web browser. A .lockbox file opens on yuzool.com/lockbox; a self-opening file opens by itself.

Is there a size limit?

Free boxes go up to 100 MB. Lockbox Pro ($1.99, once) locks bigger boxes; on a computer several GB work. Phones may run out of memory above about 500 MB.

Can someone change the file on the way?

Not without it being noticed. Every 1 MB of the box is checked when it’s unlocked, and a changed, cut-short or reordered box refuses to open.

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