Timelock: time-lock encryption for messages and files
Updated
Time-lock encryption locks data so it can be decrypted only after a set time, with no one holding the key in between. Postdate's Timelock encrypts the key for a future round of drand, a public randomness network, so the link opens only when that round is published.
Share the link today. Keep the message and files closed until the time you choose, with a key encrypted for a future release.
Use Timelock when your opening time is settled and you want encryption to enforce the wait. Choose Basic if you need a private delete link.
Create a Timelock Postdate$3 USD once. Up to 100 MB and one year. No sender delete link.
How time-lock encryption works
Timelock relies on drand, a public randomness network run by independent organizations called the League of Entropy. Every 3 seconds, drand publishes a numbered round: a random value with a signature.
Each round's signature is made jointly. A minimum number of operators, called the threshold, must each add a share, and no single operator can make it alone. They add their shares when the round's time comes.
Timelock builds on that schedule. Your browser encrypts your message and files, then encrypts their key for the round at or just after your opening time. Only that round's signature can unlock the key, so the link stays closed until drand publishes it. Not even Postdate can open it early.
The opening time is rounded up to the next scheduled release, so access can take a few extra seconds. Once that release is available, the recipient's browser can unlock the key and decrypt the content.
Who you trust
Timelock depends on drand. It assumes that fewer operators than the threshold work together to make a round early, that the network keeps publishing rounds, and that the encryption stays secure. If enough operators colluded, they could make a future round's signature before its time. If too many went offline, rounds would pause and opening would wait.
Basic depends on Postdate's policy. Postdate holds the key and releases it at your chosen time. You rely on our promise not to read your content before it opens.
This protects access through the link. A sender can still keep or share the original text, files, or encryption key. Future quantum computers could break Timelock encryption; we cannot guarantee when that risk may become practical.
Choose your lock
Basic
Postdate holds the key and releases it at your chosen time. You rely on our promise not to read the content early.
You get a private delete link. Use it until the Postdate expires, including before it opens.
Free within 7 days and 1 MB. Later dates or larger uploads are $3.
Timelock
The key needs a scheduled release from drand, an independent public network, to unlock. Postdate cannot supply that release early.
You cannot delete it yourself or move the opening earlier. Choose it when the release time is settled.
$3 per Postdate, including text-only messages.
Both encrypt your text and files in your browser before upload. Anyone with the link can open them after the opening time and before expiry. Timelock's protection depends on drand and the encryption remaining secure.
Files and a countdown page
Many time-lock tools encrypt a short text inside a link. Postdate also locks files, up to 10 files and 100 MB, encrypted in your browser. It hosts the encrypted content and a countdown page with Add to calendar, so people with the link can see when it opens.
Because Postdate hosts the content, opening also needs Postdate to be available, and Postdate can remove content for abuse. The link expires after the availability period you choose.
Other time-lock tools built on drand
Several tools use the same drand time-lock scheme. Each encrypts for a future drand round; they differ in what they take and who keeps the ciphertext.
| Tool | What it is | Files | Ciphertext kept by | Price | Open source |
|---|---|---|---|---|---|
| Postdate Timelock | What it isA hosted link with a countdown. | FilesUp to 10 files, 100 MB. | Ciphertext kept byPostdate hosts it. The key needs a future drand release. | Price$3 once. | Open sourceNo. The code is not published. |
| tlock | What it isA Go library and the tle command-line tool. | FilesAny file. | Ciphertext kept byYou. | PriceFree. | Open sourceYes, Apache 2.0 or MIT. |
| tlock-js | What it isA JavaScript library. | FilesAny data. | Ciphertext kept byYou. | PriceFree. | Open sourceYes, Apache 2.0 or MIT. |
| Timevault | What it isA browser tool from the drand team. | FilesOne file in its report mode. | Ciphertext kept byYou copy it. | PriceFree. | Open sourceYes, Apache 2.0 or MIT. |
| Flowvault | What it isA hosted note in a notepad suite. | FilesText only, up to 128 KiB. | Ciphertext kept byFlowvault. | PriceFree. | Open sourceYes, MIT. |
| TellYouLater | What it isA link that holds the ciphertext itself. | FilesText that fits in a link. | Ciphertext kept byThe link itself. | PriceFree. | Open sourceThe source is public, with no license file. |
Checked on each tool's own pages and repositories on .
Before you send
- Check the date and timezone. You cannot reschedule an existing Postdate.
- With Basic, you can delete the link and create another if plans change. Timelock has no sender delete link.
- Opening requires Postdate and drand to stay available. An outage can delay access; a shutdown could prevent it.
- Postdate can remove content for abuse. Expiry removes access through the link, but people can keep files they already downloaded.
The price
Timelock Postdates are $3 USD each, paid once. That covers up to 10 files and 100 MB total, including encryption and packaging, with an opening date up to one year away.
Choose an opening time at least 5 minutes away. After opening, keep the link available for 1 hour, 1 day, 7 days, or 30 days. The default is 7 days.
You can attach files without a note. Text notes accept 10–100,000 characters. You see the total before you create the link.
Sources
- drand security model: who runs drand, how the threshold works, and what happens if operators collude or go offline.
- tlock: Practical Timelock Encryption from Threshold BLS (IACR ePrint 2023/189): the paper behind the time-lock scheme Postdate uses.
Try it with your files
Prepare a product launch package or follow the file-sharing walkthrough. Both show how to share one link before the files open.
Read more about how Postdate works or browse all examples.