[tor-dev] GSoC project idea: pluggable transport that hides data in TCP SEQ numbers / UDP SRC ports

[Jacek Wielemborek]

Hi,

I recently had an opportunity to watch David Fifield's lightning talk on 
pluggable transports that he gave on 30C3. I find the topic fascinating and I'm 
considering an application to your project for the upcoming Google Summer of 
Code.

My idea is a bit complicated - I'd like to create a pluggable transport that 
hides data in TCP sequence number gaps or UDP source port numbers. I don't yet 
have all details thought over, but the way I imagine it right now, the user 
would have to establish a TCP or UDP connection to the relay. The connection 
could be completely bogus, though it'd be useful if a lot of data was sent 
over it. After connecting, the client sends to the server a message with a 
random RSA key steganographically hidden in the TCP sequence numbers. If the 
server replies the same way with an RSA-encrypted AES key, the rest of the 
hidden transmission goes encrypted with it. Since the SEQ number gaps are 
meant to be random anyway, I believe that this could be very hard to detect.

Obviously, this is a very difficult project. I'd like to point out that I 
already have some experience in both GSoC (worked for Nmap Project last 
summer, David Fifield was my mentor) and C programming. I imagine that I'd need 
to create some kernel-to-userspace interface that would let me do the packet 
manipulation - I'd probably start my research by looking at how OpenVPN 
implements this kind of stuff as it supports all major platforms.

The main question is - would you be interested in mentoring such a project 
during the upcoming summer?

Yours,
Jacek Wielemborek
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