Secret Box

Self-custody encryption

Lock anything. Only you hold the key.

Any file — photo, video, document — turned into unreadable ciphertext.

Start freeSee how it works

Encrypted on your device. Your key never leaves it — not even we can read your files.

A single key sits at the centre of your device. Around it, every kind of file — a photo, a video, a document, an audio clip, an archive — is continuously drawn inward and, the instant it reaches the key, turns into unreadable ciphertext that settles and dissolves there. Nothing ever travels back out toward the edge. The key never moves and never leaves: only you hold it, and we store only scrambled data we can't read.
  • Only you hold the key — we store ciphertext
  • Audited crates — no hand-rolled crypto
  • The same .rbx opens in the browser and the CLI

Try it now

Don't trust us. Run it.

Lock a real file right here in your browser — and watch the network monitor stay at zero.

Waking the engine…

One key, many uses

Pick what you need.

Same trust underneath. Start with one — add more anytime.

Available now

Lock a file with a key only you hold.

Sealed on your device in your browser — free, no account needed to try.

Available now

Let your AI agent act — without seeing your secrets.

Your agent works by label only. Values stay sealed; you approve each use, and everything is audited.

Open it at the right time.

Seal a file until a date you choose. No one opens it early — not even us.

Never get locked out.

Split your key into shares for people you trust — any 3 of 5 bring it back.

Store it where we can't read it.

Keep sealed boxes in your cloud vault. We hold ciphertext only.

How it works

Three steps. Under a minute.

  1. 01

    Pick what to protect

    A file, a note, a whole folder. It never leaves your device unprotected.

  2. 02

    It's sealed on your device

    Encrypted right here with a key only you hold — something you remember, or a key file you keep. Then back it up: we walk you through it.

  3. 03

    Only the right key opens it

    Store the locked file with us, or download it. It's worthless to anyone without your key.

Built for the agent era

Your AI agent acts — without seeing your secrets

It asks, you approve, the value routes from your vault to the page — around the agent. Every step is audited.

Diagram: an AI agent asks Secret Box to fill the card-number field. The value stays hidden from the agent. Policy resolves to ask; you approve; the value routes from the vault directly to the page, bypassing the agent; and an audit row records the action.

Time-locks

Enforced by a public beacon

A time-locked file opens at a drand round that no one — including us — controls.

current round

Current drand round. It increments every three seconds while this section is visible.

reaching the beacon…

a public beacon no one — including us — controls

a file locked to next week opens at round ~— ——— ———

The honest part

“But what if I lose my key?”

It's the right question — and the scary one. So we don't leave it to chance. When you lock something, we help you set up a backup in under a minute: print an emergency kit, or split your key into pieces so trusted people can help you recover it — while no single piece (not even ours) can ever open your files alone.

We can't read your files — ever.

Here's how you get back in: your recovery key, or any 3 of your 5 trusted shares.

The split uses Shamir's Secret Sharing and happens on your device. Give one share to each person or place you trust: any 3 of 5 together can recover your file, fewer than 3 reveal nothing — and we never kept the key.

See how recovery works

Shamir's Secret Sharing

One key, five shares

Any 3 of 5 reopen it. Fewer than 3 reveal nothing — and we never kept the key.

fewer than 3 reveal nothing

vacation.rbx
Animation: one key splits into five shares. Any three converge to re-form the key and the file unlocks; the other two stay dim — fewer than three reveal nothing.

Why trust us

Don't trust us. You don't have to.

Security shouldn't be a promise. It should be something you can check.

Only you hold the key

Your files are locked with a key that stays on your device. We store only scrambled data we can't read.

Built on audited cryptography

XChaCha20-Poly1305, Argon2id, Shamir — standard building blocks that the wider security community has already reviewed. We orchestrate them; we never invent our own.

Even a court can't make us open it

When you hold the key, we simply don't have what it takes to open your files — on purpose.

Survives us

You can always download your locked files and keys. If we disappeared tomorrow, they'd still open for you.

Pricing

Locking files on your device stays free. Forever.

Pay only for what lives beyond your device — storage, time-locks, and family access.

Free

On-device locking, forever.

$0

No card. No catch.

  • Included:Lock unlimited files on your device
  • Included:Recovery kits & Shamir shares
  • Included:200 MB sealed cloud storage
  • Included:Agent keys, approvals & audit log
Start free
Most useful

Personal

Your vault, beyond one device.

$4/month

billed monthly

  • Included:Everything in Free
  • Included:50 GB sealed cloud storage
  • Included:Time-locked vaults
  • Included:Private fields & policies, unlimited
  • Included:Priority support

Family

For the people who'd need to get in.

$8/month

billed monthly

  • Included:Everything in Personal
  • Included:Up to 5 family members
  • Included:Digital inheritance
  • Included:Shared recovery for trustees

Paid plans aren't on sale yet — Free is the whole product today.

Questions

The things people actually ask.

No. Files are locked on your device with a key only you hold. We only ever store scrambled data we have no way to read.

If you have no backup, the file is gone for good — that's what makes it truly private. So we help you set up recovery up front: an emergency kit, or splitting your key among people you trust.

You can always export your locked files and keys. The engine ships as a CLI you can keep: the same .rbx file your browser makes opens on your own machine, with no servers and no account. Even if we vanished tomorrow, your files would still open for you.

It's built on cryptography that independent security firms have audited — not something we invented ourselves. And only you hold the key, so even we can't open your files. You can even watch in your browser that nothing leaves your device unscrambled.

Locking files starts free. You only pay for extras like long-term storage, time-locks, or inheritance — and you can cancel anytime.

Lock your first file in under a minute.

Free, on your device, no card — and your backup set up before you're done.

Start free