Sorry to burst your delusional bubble, but you don't need to break encryption in this case. The term to describe this particular "attack" is traffic analysis,

Sorry to burst your delusional bubble, but you don't need to break encryption in this case. The term to describe this particular "attack" is traffic analysis, and it is a real bitch to get around. P2P protocols will not end up looking like HTTP requests and responses because the nature of the information flow is nothing like a standard HTTP exchange; you do not send a small packet, get back a large chunk, and then exchange small updates -- when P2P traffic flows it is large chunks and its bidirectional nature is a dead giveaway. The application of a simple Bayesian recognizer to categorize traffic flows might be new to the academic community, but among people developing large-scale traffic management and security monitors this is really old stuff.