Far too much yap yap yappin' around here lately.. cpunks write code,
   remember? Let's get back to business.
   Here's an idea for a private, censorship-resistant communication/file
   sharing system with integrated invitations and access control. I don't
   think I've ever seen this before, but it's quite possible that people
   have discussed this idea previously. Either way, I don't know of any
   implementations yet.
   Problem
   =======
   The current P2P file sharing landscape is divided up into two spaces:
   1) private tracker communities ([1]what.cd // Demonoid // etc) which
   provide high quality network speeds and file quality through
   moderation, but which are often subject to outages due to
   centralization, and 2) the single giant BitTorrent 'peer exchange'
   distributed hash table, which provides universal file access and
   fault-tolerance, but at the cost of abuse and surveillance of those
   participating.
   Ideally, we want a peer-to-peer community which is decentralized and
   fault-tolerant, but with enough authority to maintain a high network
   quality and private enough to avoid open surveillance.
   Proposed Solution
   =======
   It might be possible to combine the exclusivity and moderation of
   private trackers with the fault-tolerance of distributed hash tables by
   having each private table operate with a certificated-authority based
   public key infrastructure. Essentially, to participate in the DHT,
   peers must cryptographically prove that they have been invited to
   participate.
   Power and trust flow down a through a concentric certificate web. A
   client's authority in the network is a function of how far away from
   the root authority they are (not dissimilar to Scientology's
   hierarchy.) Clients should automatically respect commands coming from
   those higher up the cert chain or from those closer to the root than
   they are, and should listen to, but not automatically respect, commands
   from those lower down the cert chain or from "lower-ranking" clients.
   * Bootstrapping and Invitation
   The very first user of the network will have to generate a root
   certificate. He is then able to generate new signing certificates,
   which he can give to new users of a network to allow them the ability
   to access the network. These new users should be able to use their own
   certificates to do the same for their own new users. (This could be
   done with certificate signing requests coming from potential new users
   as well, but that might come at the cost of a slightly more complicated
   user experience).
   * Revocation
   Bannings can be performed by issuing updates to a network-wide
   revocation list. Clients will automatically respect revocations coming
   from superiors, and may or may not choose to respect revocations coming
   from underlings.
   * Implementation
   Everything needed to create the heart of this should exist already in
   Kademlia and OpenSSL. BitTorrent could serve as the basis for the
   file-sharing application, but vanilla BitTorrent has a content
   discovery problem, so I'd suggest that any implementations of
   BitTorrent on Private Distributed Hash Tables should have some kind of
   discovery BEP included as well, possibly one which uses the authority
   system of the PDHT to verify files. There's also a possibility there
   for what you might call "trusted amnesia" - the ability for a user with
   a high authority to publish verified documents to the whole network
   without having to broadly expose themselves as the source of the
   content by having peers in their same trust level sign their content,
   forget the source, then increase the availability by one access level.
   Anyway, that's the sketch. Any thoughts?
   Rich

References

   1. http://what.cd/