A letter for later
Words for your child on their eighteenth birthday, written today and unreadable until the morning it arrives.
A safe that obeys time
Keep your documents encrypted until the moment you choose.
Time-Secret turns your files into a vault that stays locked until a date you set. No account, no upload, and nobody can open it early — not us, not the person holding it, not any government.
For-Alex.2035.html
Encrypted
Vault
For-Alex.2035
Sealed on
14 Aug 2026
Opens on
01 Jan 2035, 00:00 UTC
To open
The date + 12 words
Opens in
—
days
—
hours
—
min
—
sec
Until then, this file is unreadable — even to whoever is holding it.
An example vault. This is the real screen, not a mock-up.
What it's for
Some things are only meant to be read later.
A sealed envelope you cannot steam open. You decide the date; time does the rest of the work.
What your family will need
Where the will is kept, which accounts exist, how to reach the notary. Sealed now, opened when it is time.
A document under embargo
Results, an announcement, an investigation. Distribute the file in advance and it still cannot be read before publication day.
A message you may never send
Give a copy to someone you trust. If the date comes, they can open it. If it never comes, nobody ever read a word.
How it works
Three steps, on your own computer.
You open one file in your browser. Nothing is installed, nothing is sent anywhere — you can unplug the internet and it still works.
Choose
Add one or more files and pick the date and time the vault should open.
Protect
Keep the recommended twelve-word code, so the date alone is not enough — or rely on the date if the file may become public that day.
Keep
Save the vault, print the paper sheet with the twelve words, and give them to whoever should receive them.
Why it cannot be opened early
Two locks. Both have to give way.
Most "locked until" products simply ask a server to say no. Time-Secret has no server to ask, and no key to hand over.
The time lock
A public network of independent servers called drand publishes a new, unpredictable number every three seconds, forever. Your vault is locked with the number belonging to a moment in the future.
That number does not exist yet, and nobody can work it out ahead of time. Not us, not you, not somebody who steals the file, not a court order.
This is the lock that expires.
The knowledge lock
Twelve ordinary words, shown to you once and printed on paper. They are never saved, never sent, and never stored inside the vault file.
Whoever does not have them never opens the vault — not on the date, not a century later. A stolen copy stays a meaningless block of noise.
This is the lock that never expires.
The time lock is what expires. The knowledge lock is what makes the vault yours, rather than the public's, once it does.
Changing your computer's clock changes nothing. The date is checked against drand's public signature, not against your machine. Rolling the clock forward just produces an error.
What you actually get
Made to outlive this website.
Time-Secret is not a service you subscribe to. It is two files, and neither of them needs us to still be here.
The vault maker
time-secret.html
A single web page saved on your computer. Open it, and it encrypts your files right there. It never sends anything, and it cannot open vaults — it only makes them.
Your vault
For-Alex.2035.html
Another single web page, with your encrypted files sealed inside it and its own unlocking screen built in. Email it, print a backup, bury it on a hard drive. Whoever opens it years from now needs nothing but a browser.
Download
One file. Free. Yours to keep.
Save it somewhere you will find it again — it is the only thing you need in order to seal a vault, today or in ten years.
Download Time-Secret- File
- time-secret.html
- Size
- 1.00 MB (997,086 bytes)
- Published
- 14 Aug 2026
- SHA-256
- d4cd59b9e8b2f875bda27528041b99290fd09b0638970d8861308591f9f700ed
Careful? Check the file you received matches:
shasum -a 256 time-secret.html.
How to open it
- Save the file to your computer — your Downloads folder is fine.
- Double-click it. It opens in your web browser like any web page.
- That's it. You can disconnect from the internet first if you want to; sealing a vault never needs a connection.
Use a computer, not a phone. Tapping the file inside Mail or WhatsApp only shows a preview, which displays nothing useful. And Safari on iPhone and iPad cannot open a saved file at all. Move it to a Mac, Windows or Linux machine.
Before you rely on it
What Time-Secret will not do for you.
Encryption this strict has consequences. Better to know them now than on the opening day.
- No reset
- Lose the twelve words and the vault is gone forever. There is no copy, no support desk, no recovery. Print the sheet and store it somewhere safe.
- Date is final
- Once sealed, the opening date cannot be moved — not earlier, not later. If you need a different date, seal a new vault.
- Not a backup
- Time-Secret keeps nothing. If your only copy of the vault is lost, so are its contents. Keep several copies in different places.
- Name is public
- Anyone holding the file can read the vault's name and its dates — that is how they know what to do with it. Do not name a vault after what it contains.
- Size limits
- Up to 5 MB per file and 50 MB in total. Everything is encrypted in your browser's memory, which is what keeps it off any server.
- After opening
- Once the vault is opened and the files are saved, they are ordinary files again. From that point, normal care applies.
Questions
Plain answers first, technical details last.
Where do my files go?
Nowhere. They are encrypted inside the page open on your screen, and the finished vault is saved straight to your disk. Creating a vault makes no network request at all — you can prove it by disconnecting first.
There is no Time-Secret server. There is nowhere for a file to be sent.
What really stops someone opening it early?
The key needed to open it does not exist yet. It will be published by the drand network at the moment you chose, and not one second sooner.
This is not a rule that software chooses to enforce, and it is not a password someone could be pressured into giving up. Nobody on earth holds that key today — including us.
Why does opening a vault need the internet, if sealing one doesn't?
Only to fetch that public key from the drand network once the date has passed. It is a public number that anybody can request.
Your vault and your twelve words are never sent anywhere. The decryption itself happens on your own machine.
What is the difference between the two protection choices?
Date + twelve words (recommended) needs two independent things. A stolen vault is useless without the paper, forever.
Date only means that once the date passes, anyone holding a copy can open it — a forwarded email, an old cloud backup, a shared computer. Choose it only if the contents may become public that day.
I lost the twelve words. What now?
The vault can never be opened. We are not being unhelpful: we genuinely never had them. They are shown once, never saved, and never written into the file.
That is the same property that makes a stolen vault worthless.
What can someone see without opening it?
The name you gave the vault, the date it was sealed, the date it opens, and some technical version numbers. That is deliberate — it is how a recipient knows what the file is and when to come back.
The original file names and their contents stay encrypted. Again: do not name a vault after what it contains.
What if Time-Secret disappears?
Nothing changes. Every vault is a self-contained file that carries its own unlocking screen inside it. It does not call this website, and it does not need us to exist.
The code is open source, so anyone can rebuild the tool or write a compatible one from the published format.
Can I change the date after sealing?
No. A vault set for a graduation must not quietly slide to another day — so once sealed, the date is fixed. If you need a different one, make a new vault.
How much can I put in a vault?
Up to 5 MB per file, and 50 MB per vault. Everything is encrypted inside your browser's memory, which is precisely what lets it work without a server.
Documents, photos, spreadsheets and keys fit comfortably. Video does not.
Can I use it on my phone?
Not reliably, and on iPhone or iPad not at all: Safari cannot open a file saved on the device. Tapping an attachment in Mail or WhatsApp only shows a preview, which cannot run the vault.
Use a computer. If you receive a vault on a phone, forward it to a machine that can open it.
Is it really free?
Yes. It is free, open source under the MIT licence, has no account, no tracking and no analytics. There is nothing to sell you, because there is no service running.
Which cryptography is used? Technical
Files are compressed and encrypted with XChaCha20-Poly1305 under a random key. That key is time-locked with tlock — identity-based encryption toward a future round of the drand quicknet chain, which produces a BLS signature every three seconds.
The twelve-word code is BIP39, stretched with Argon2id. Every drand signature is verified against a chain public key pinned in the app, so a hostile mirror can withhold data but cannot forge an early unlock.
The file format is documented and versioned so a conforming implementation can still open your vault in ten years. Read the source and the format specification.