protocol.txt

Groundhog Protocol Version 1

Note
    This memo describes specifications of Groundhog Protocol Version 1. Since
    such protocol cannot be considered mature at this time. Protocol
    specification may change without updating version number. That is, there may
    be multiple Groundhog Protocol Version 1 standards, but only the latest one
    should be followed.

1. Introduction
    Despite the Internet has connect almost everywhere on Earth, in many cases,
    network traffics are monitored or control by firewalls for various reasons,
    including, but not limited to, computing system security and censorship.
    Groundhog is a transparent protocol exists to solve this issue. By using
    this protocol, network traffics are encrypted and rerouted before reaching
    target host, without modifying any underlying protocol, such as HTTP, SMTP,
    and FTP. Although all traffic still go through firewalls, firewalls are
    unaware of content and destination of traffics.

2. Weakness
    As for the least version 1 protocol, there are 2 major weaknesses/flaws.

    i. Groundhog traffic has a particularly identifiable characteristic. The
    first 550 bytes of a TCP connection is always a 4096-bit PublicKey in PKIX
    format. Although contents are still secured, a firewall can easily identify
    Groundhog and reset the corresponding connection. In future versions, this
    might be solved with a server-wide PSK obfuscation. The goal is making
    connection implementing Groundhog protocol indistinguishable from random
    byte stream.

    ii. Each Groundhog connect has a significantly large overhead, and 3 RTT is
    required before actual data transmission can begin. Before data transmission
    can begin, server and client must exchange 4096 bit RSA public key (550
    bytes for PKIX formatted public key), taking 1 RTT. In addition, a further
    512 bytes is used for request, 512 bytes for response. Actual data
    transmission begin on the 3rd RTT (after 16 bytes of IV received). This
    issue can be solved by using a server-assigned token and AES key after the
    first connection established, but which is against the goal of making
    Groundhog protocol indistinguishable from random-byte stream.