Protocol

payload

-> 

n | padding | m | payload

• n (word32be): the number of bytes of padding
• padding: n bytes of noise
• m (word32be): the number of bytes of the original payload
• payload: the original packet

Implementation

• n is deduced from a randomly generated i = n + m for each packet.
• When a random i is less then m, payload is split to p1 and p2 to satisfy the constrain, where the length of p1 is equal to i and p1 + p2 = payload. p2 will be sent in the next iteration by the same algorithm.
• i is bounded by a maximum r, configurable by the --randomnessInBytes argument.
• To reduce overhead, n is set to 0 whenever m is greater then r.

Usage

• local:

    neko-obfs --localHost TEXT --localPort INTEGER --remoteHost TEXT --remotePort INTEGER
  

• remote:

    neko-obfs --role remote --remoteHost TEXT --remotePort INTEGER --forwardHost TEXT --forwardPort INTEGER
  

• This tunnel should be used inside an encrypted tunnel.

• For example:

    ss-local (rc4)
  
      -> neko-obfs -> ss-tunnel (aes-256-cfb)
  
        -> gfw -> internet
  
      -> ss-tunnel (aes-256-cfb) -> neko-obfs 
  
    -> ss-server (rc4)
  

• Note it's the ss-tunnel layer that protects the obfuscation, otherwise data and noise length are clearly visible.

Performance

• No noticeable slow down yet (Jul 24, 2017)