Send files with a one-time encrypted link
Send a file of up to 500 MB with a link that can be downloaded only once and expires within an hour. It is encrypted in your browser before upload.
A roller conveyor carries a locked crate from one end to the other, passing under a store with four columns and a lamp. Behind it, on a separate track, travels a small key that never goes through the store. Enter, Space or the arrow keys move from one step to the next.
How to use it
- Choose the file or drag it onto the dashed area: up to 500 MB.
- Choose how long it waits to be downloaded: 15 minutes, 30 minutes or 1 hour.
- Click “Encrypt and create link” and send the link to whoever should get the file. Once downloaded, it is deleted.
Frequently asked questions
Can you see the file I send?
No. It is encrypted in your browser with 256-bit AES-GCM before it is uploaded, and the key goes in the part of the link after “#”, which browsers never send to the server. We only store the encrypted file.
How many times can it be downloaded?
Only once. As soon as someone downloads it, the file is deleted from storage and the link stops working. If nobody downloads it, it can no longer be opened once it expires, at most one hour after upload, and it is deleted from storage by the next day at the latest.
Is there a size or sending limit?
Each file can be up to 500 MB, and from the same connection you can send 10 per hour, 30 per day and 2000 MB per day. To count them, an irreversible fingerprint of your IP address is kept for 48 hours at most.
Where is the file stored?
Encrypted, in Cloudflare R2 storage, until it is downloaded or expires. Without the key in the link it is a meaningless string of bytes, for us and for Cloudflare too.
What if someone intercepts the link?
They could download it before the recipient, because the link carries the key. But then the recipient will see that the file no longer exists and will know someone got there first.
How encrypted sending works
When you click the button, your browser generates a random key and uses it to encrypt the file and its name, with 256-bit AES-GCM. Only then does it upload the result to storage, directly and without passing through our server. What is stored is a string of encrypted bytes that cannot be read without the key.
The key goes in the part of the link after “#”, the fragment, which browsers never send to the server. Whoever opens the link downloads the encrypted file and their browser decrypts it with that key: neither we nor the storage provider can see what you sent.
When to use it and when not to
It is for sending a document that will not fit in an email, some photos, a contract or a small backup, without creating accounts or leaving the file sitting in a cloud. It is deleted as soon as it is downloaded; if nobody downloads it, it can no longer be opened after an hour at most and is deleted from storage by the next day at the latest: no forgotten copy is left anywhere.
The link only works once, so tell the recipient not to open it on another device just to try it. If someone intercepts the link and downloads it first, the recipient will see that it no longer exists and you will both know someone got there before them. For small things, such as a password, the secret link is handier, as it shows the text on screen.
Limits of the service
Each file can be up to 500 MB. It is encrypted whole in the device’s memory, which can take up twice the size of the file: on a computer that is not a problem, but from about 100 MB upwards it may fail on a phone. The same goes for whoever downloads it. If you need to send more, split it into several files.
From the same connection you can send 10 files per hour, 30 per day and 2000 MB per day, and the service’s total space is limited: if it ever fills up, wait a few hours for other transfers to expire. Files that nobody downloads are deleted at most one day after they expire.
