alternatively, you could create a free account at
http://tracker.conspiracycentral.net/
it's a bitorrent community, and a great one. i recommend using
utorrent.
then you would have access to thousands of already-seeded files
i like your idea, but then again there's no need to reinvent the wheel when a pretty round one already is out there for us to use!
cheers.
edit: i understand one of the criteria is to have a serverless and private exchange medium... but honestly, any sufficiently motivated group of people with access to the right technologies can literally get into anything they want, so going overboard with security is not really that necessary if you are just exchanging information. what are you gonna be peer-to-peer'ing anyway? unless it's bank account information or your medical history, a file sharing service is much easier, much more widely available, and offers more access to the types of peers who are ready, willing and able to exchange information like you.
nothing against the community here, but not many of avalon's members are techie nerds that need or even want a service like the one you are setting up (not that it isn't understood and appreciated by some of us!)
i hope this post was of some value to ya. take care bud.