BitTorrent Sync: like Dropbox, but fully peer-to-peer and private

Ars Technica's Jon Brodkin reviews the new BitTorrent BitTorrent Sync, a peer-to-peer-based Dropbox replacement that's now in public alpha testing. BTSync uses the BitTorrent protocol to keep the files on several computers synchronized, and the actual file-transfers are robustly encrypted so that no one -- not BitTorrent Inc, not your ISP, and not a hacker -- can sniff them as they traverse the Internet and invade your privacy. There's no central server for the police to seize or for hackers or backhoes to knock offline, either. Brodkin's review is comprehensive and makes this sound like a hell of a product.

"Since Sync is based on P2P and doesn’t require a pit-stop in the cloud, you can transfer files at the maximum speed supported by your network," BitTorrent said. "BitTorrent Sync is specifically designed to handle large files, so you can sync original, high quality, uncompressed files."

In the pre-alpha testing that began in January, 20,000 users synced more than 200TB of data. BitTorrent Sync clients can be downloaded now for Windows, Macs, Linux desktops, and Linux-based network-attached storage devices. Mobile support will come later.

Setting the client up is easy. No account is required, but a randomly generated (or user-chosen) 21-byte key is needed to sync folders across computers. After installing the application and choosing a folder to sync you'll be given a string of random letters and numbers that should be typed into a second computer to sync the folder...

BitTorrent Sync creates private, peer-to-peer Dropbox, no cloud required


  1. I use Dropbox with the full understanding that it isn’t secure and isn’t necessarily private, because it is both using cloud storage out of my control and it is a closed system that I cannot realistically investigate.  BitTorrent Sync certainly puts the first concern to rest, but the second?  Not so much at all, and I have a hard time putting any significant amount of faith in privacy or security in the hands of a company whose name is essentially synonymous with “illegal distribution of copyrighted works” to many people.  

    I find that it is difficult to trust, with that reputation so closely associated with them, that they are neither in full cooperation with agencies seeking to diminish user privacy nor unscrupulous about your data themselves.  It’s unfortunate, since I’m excited about the technology and implementation behind it.

    1. I don’t think I’m understanding you, Justin.  You don’t feel that a company with a long-established reputation for deadly opposition to user-privacy-diminishers can be trusted not to be in league with those same diminishers?  Who WOULD you trust to protect your privacy, if not people whose livelihood depends on privacy?

    2. synonymous with “illegal distribution of copyrighted works” to many people

      Yeah… it’s how I download Democracy Now broadcasts from this sekrit location here:

      And, all the other horrible things I do with the technology like download ENTIRE Operating Systems from this sekrit place here:

      I also use a cell phone knowing full well that phones are known by many people to be used with the illegal distribution of drugs.

      I feel so rotten.

    1. Depends on how many nodes you are dealing with. Bittorrent’s main virtues start to come into focus when you need to distribute something to quite a few locations(since it makes it trivially easy for others in the swarm to act as mirrors, without the need to have all the data, configure an HTTP server, etc.)

      If you are just syncing pointA and point B, rsync is a tough act to beat. If point A has something that points 1-10,000 need to have, letting them chip in for some of the bandwidth is a fairly handy feature.

  2. I think whether or not this is more useful than Dropbox or a similar service is what your needs are and what infrastructure you have in place. My primary need is backup. I *want* encrypted backups of my half-assed writing projects on Dropbox. If my house burns down with my laptop and my backup machine still in it, my data is still protected. 

    If I have a machine at a colo facility to sync with, however, this BTSync thing makes much more sense to me. I’m protected against disaster and I have an easier time maintaining privacy. 

      1. Strictly speaking, neither service is architecturally well-suited to ensuring privacy of files off your computer.

        It’s just that dropbox pretends that it is so suited, while the design(assuming it is in fact implemented as claimed) of this bittorrent-based system encrypts the file before it leaves your system, so only people you’ve shared the key with can make use of it.

        If you were to use dropbox exclusively to handle and synchronize files that you encrypted yourself ahead of time, you would be similarly mostly safe; but they don’t exactly encourage that(nor is it even possible in environments like ‘tablet applications that integrate with dropbox directly; because the ‘Hey, let’s just hide the filesystem entirely!’ model makes file transfer a pain in the ass).

        As a protocol, bittorrent is more or less overtly public(even ‘private trackers’ are a substantially broken ad-hoc hack, and once the DHT comes into play, forget it. On the plus side, this more or less requires that anybody attempting private file distribution atop bittorrent do adequate client-side encryption.

        With more conventional services, that can take advantages of point-to-point SSLed connections, the wrapper helps protect you from the man in the middle; but also lets you do idiotic things like ‘use the same encryption key for every customer’s data, when at rest’.

      2. Like I said, I encrypt my backups (and anything else I want to keep private on Dropbox). I’ve worked in IT long enough not to actually *trust* them.

    1. “I think whether or not this is more useful than Dropbox or a similar
      service is what your needs are and what infrastructure you have in
      place. ”

      For me the coolest thing about Dropbox is that it keeps git-style backup versions of files for 30 days. If I screw something up or accidentally delete a file beyond recovery I can go to Dropbox’s website and get a version from a few hours or a few days ago.

      This has saved my butt several times.

  3. This would be handy for installing linux from. Boot a minimal image, then get all the files from your install from a read only key of this, from everyone else who installed this way.

      It isn’t a default; but debian offers install media that are essentially ‘just enough base system to get apt running’ and (as the name suggests) ‘apt-transport-debtorrent’ is a pluggable transport for apt that retrieves packages over bittorrent(as opposed to the more typical apt-transport-https). It’d be reasonably doable to respin the minimal install medium to include this as the default apt transport, if one were so inclined…

  4. I don’t understand why Dropbox was chosen as the model for what Sync does.

    Dropbox provides cloud-based hosting of files, rendering them available 24/7.

    BT Sync lets you distribute files between machines when and only when someone in the pool of peers actually is online, and has the file(s) you need.

    Big difference, especially if you use Dropbox primarily to move files between a small number of people…!

    Nice extension of the technology; not a Dropbox replacement by any analysis.

  5. I find this a brilliant concept and am testing the thing now. I’m running a video production company which relies heavily on outsourced content and have a real problem shuttling and syncing 50+ gb project files with all the people involved. So far I’ve relied on the good old “hd-in-a-bag” transfer protocol but I’m willing to give this a go. We’ll see how it pans out…

  6. Is there a GPL / Free Software / “Open Source” licensed software such as bittorrent-sync?
    A similar software offering self-hostet tracker would be marvellous!

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