Tresorit Send - Secure File Sharing Service
Before I get started, let me just say this upfront: no this is not a sponsored article, nor are there any paid ads or affiliate links in here.
Some time back, I was looking for a simple, secure file sharing service to deliver files to my clients. I might have multiple file deliveries with overlapping download durations, so typical methods like using Google Drive or Dropbox to generate shared links were not feasible unless I upgraded to a paid plan with way more storage.
In Japan the de-facto file sharing service is called Gigafile, which I shall not link here as I personally am totally not fond of it - ads are everywhere on the site, and I have never managed to find any notes on how uploaded files are encrypted or secured so I just assume it is non-existent.
That was when I stumbled upon Tresorit Send. Tresorit provides secure cloud storage solutions, with extra emphasis on security, and Tresorit Send is a free standalone product provided by them that uses similar underlying technologies in their secure cloud storage solutions.
While you do not need an account with Tresorit to use Tresorit Send, a valid e-mail address is required during upload (for admin control, more on this later).
The way to use it is pretty straightforward - simply select your files through their website or browser plugin, fill in your e-mail address, add password protection if desired, and start the upload process.
(Side note: I do recommend the browser plugin - makes the entire process more seamless)
The files are encrypted locally on-the-fly as they are uploaded, and when the upload process is completed, a URL is generated for sharing. Both the path to the files and the decryption key are embedded in the generated URL, and as a user accesses the shared URL, the files are decrypted on-the-fly as they are being downloaded.
If password protection was selected during upload, the user accessing the shared URL must key in the password before being able to start the decryption process.
An admin link is also sent to your e-mail address which allows you to check how many times the file has been accessed, as well as to revoke the link any time. It is important to note that the admin link does not contain the link to the actual file in any manner (for security reasons), and as such if you lose the original generated URL your only way is to just re-upload and get a new URL.
More in depth information on the service and its technologies can be read in their FAQ here.
Being a free service it does have certain limitations and restrictions:
Maximum total file size is 5GB per link.
Maximum number of files is 100 per link.
Each link can only be accessed 10 times.
Each link is only active for 7 days.
Admin links only show number of downloads, not detailed statistics like IP addresses.
The service is only available in English, which may matter to some users.
While you can circumvent the maximum file number limit by zipping up your files prior to upload, removing the other restrictions and limitations (except for the English language only restriction) would require you to subscribe to their cloud storage solutions and using it to generate a secure link.
To be fair, 5GB/link is really generous for a free service, and the duration of the active link is decent too since most of my clients would download it within a few days upon receipt.
However, a certain OS (from a certain fruit) does sometimes not show when a file is downloading, especially when using an embedded browser, so there are instances whereby my clients just spammed the download button and exceeded the 10-times download limit unknowingly within seconds.
Anyway, something to take note of is that since encryption and decryption happens locally on-the-fly, for large files it is actually a pretty resource intensive process, so depending on your machine’s/device’s specs it may take much longer than anticipated to upload or download a file.