Perhaps the company’s most important innovation since its co-founder Bram Cohen released the BitTorrent protocol in 2001, BitTorrent Sync has now entered public beta and is available to download. Sync is a free tool that synchronizes files across all of your devices (Windows, Mac, Linux, FreeBSD, Android, iOS coming soon), and also allows you to share those files with friends and family (a la Dropbox). Most importantly, though, Sync is based on the peer-to-peer BitTorrent protocol, so your files move directly from one device to another, never passing through an insecure intermediary. Furthermore, every transfer is encrypted, and people can only access your shared files/folders if they have the correct secret key — and yes, this key can be a one-time secret, enabling some very interesting usage scenarios.
BitTorrent Sync, as the name suggests, tackles one of modern life’s most pertinent problems: Syncing your photos, videos, and documents across all of your devices. First-party solutions exist, such as SkyDrive and iCloud, but these programs also save a copy to the cloud, and for various reasons, such as the NSA having access to Microsoft and Apple’s servers) and other potential security hazards, this might not be desirable. BitTorrent Sync uses 256-bit AES encryption and the BitTorrent protocol to safely and quickly move files between your devices. To share a folder, you create a secret key and input it into another device (your friend’s computer, your smartphone), and that device automatically discovers your shared folder — via DHT, PEX, local discovery, trackers — and starts syncing.
In the case that you can’t initiate a direct connection to another device, BitTorrent offers to relay the data through one of its servers — but the data is always encrypted, and you can opt out if you wish.
Every folder has a different secret key, and only devices with that secret can see that folder. Furthermore, you can create read-only secrets (ideal for sharing materials with colleagues), and one-time secrets that can only be used once (so you can be sure that other people/devices don’t re-use the key to access your files). For mobile devices, instead of forcing you to email the key to yourself or painstakingly entering it by hand, Sync pops up a QR code that you can quickly scan. If you go ahead and download Sync (download links are below), add my secret key (AMUEYTPNG5KNOLVITUAE6L75CAVXT7VW7) and you’ll instantly have access to my directory of disgustingly dirty delights.
Beyond the basics, Sync also includes some advanced features that some users might enjoy. There’s a basic versioning system, for easy access to deleted and old versions of files. There’s one-way synchronization, if you want to push files somewhere, but don’t want any changes you make to be replicated. There’s support for NAS devices (such as FreeNAS based on FreeBSD), and a fancy web-based UI for such systems (and Linux).
There are lots of really, really cool uses for Sync. At its most basic, you could use it to sync photos between your smartphone and PC, or documents between your home and office PCs. Instead of using Dropbox or YouSendIt to share assets with friends or colleagues, you could just share the secret key. If you want to share sensitive files/photos/videos with an online forum or a loved one, Sync just screams to be used. For smaller, private online communities, Sync could even replace torrents — just share your keys, and let people directly download files from your hard drive.