What kind of information can the ISP see when a BitTorrent data packet is passing through their network if BitTorrent is in encrypted mode?
According to the inventor:
The so-called ‘encryption’ of BitTorrent traffic isn’t really encryption, it’s obfuscation. It provides no anonymity whatsoever, and only temporarily evades traffic shaping.
As I’ve said before, protocol encryption is at best a temporary hack around ISP rate limiting, until identification techniques are put in place which use transfer patterns rather than packet inspection to identify traffic.
In this research paper, they
show how even obfuscated application layer protocols, such as BitTorrent’s MSE protocol and Skype, can be identified by fingerprinting statistically measurable properties of TCP and UDP sessions.