Sync, a new product from BitTorrent, Inc., has been cited as a viable alternative to other cloud-storage platforms. The Sync FAQ indicates that an encryption scheme is being used, but does not comment on specifics.

Does there exist any information about the type of encryption that BitTorrent Sync is using, and whether or not the implementation is secure?

The issue you're dealing with, here, is that if you decide not to encrypt a connection, you're making assumptions regarding the sensitivity of the data that goes over that connection.

Unfortunately, it is impossible to properly make that assumption because:


You might not have fully understood all the implication of the data (for instance, if Twitter didn't encrypt data, it could be used by government agencies to spot dissidents and opponents).
Data can become sensitive after they are being transmitted (for instance, answering "who was your first grade teacher" in a web chat with old school buddies could lead to a compromise of your iTunes account later on).


In the end, it is the same as dealing with sensitive paper documents: you can decide to shred what's sensitive only but all it takes for that model to crumble is a single mistake. It's much easier to simply destroy ALL documents securely and not worry about sorting.

Given the relatively low cost and of using connection security and the fact that it wards you against all the above problems (mostly), it makes a lot more sense to encrypt everything that to try to cherry-pick the "right" content to be encrypted.
