Shaw → Re: BT upload slowdowns in Greater Vancouver #2

Goal of the weak payload encryption is to work around
intelligent traffic analyzers looking for protocol
signatures. Two schemes are suggested for packet encryption
torrent file oriented and seed oriented In both schemes only
payload - bytes following 8 bytes request ID are encrypted.
this does not create a problem because 64 bits request ID is
 generated locally by peer and essentially floating
arbitrary random number. In both cases weak encryption is
XOR - symmetrical, fast encryption algorithm.

In the torrent file oriented scheme weak encryption key -
XOR, is part of the torrent file containing hashes
of the data. Using of XOR key for both requests and reply is
 mandatory for all peers willing to participate in the data
distribution. Rodi client opens torrent file and fetches
encryption key. Rodi client encrypt all outgoing packets
with this key.

There is no way to distinguish between requests encrypted by
 different keys - key is not part of the payload and there
is no any initial handshake-key exchange between the peers.
This scheme assumes that all peers participate in
distribution of only one file.

In the seed oriented scheme encryption key - XOR, is part of
 the host's (publisher) profile. Publisher advertises IP
range/port/public key combination on the identification
server. Publisher posts XOR key of arbitrary length as an
ASCII string.

When packet arrive to the publisher publisher runs
decryption and attempts to parse the packet. If publisher
finds that the packet is not encrypted publisher can
optionally attempt to parse unencrypted packet or can discard the packet.

On the client (downloader) side user adds host and host's
encryption key to the data base of hosts. When download
subsystem  issues request Rodi client will look for the
destination peer in the table of peers and if encryption is
required packet builder encrypts the payload.

Torrent oriented scheme is more flexible and will be
implemented first. One of other options that encryption key
can be published on the message board as part of the data
advertisement or it can be the same permanent or randomly
changed key used by this specific group of content
publishers - publishers belonging to the same Rodi House.