This is a look-like nothing obfuscation protocol that incorporates ideas and
concepts from Philipp Winter's ScrambleSuit protocol. The obfs naming was
chosen primarily because it was shorter, in terms of protocol ancestry obfs4
is much closer to ScrambleSuit than obfs2/obfs3.
The notable differences between ScrambleSuit and obfs4:
* The handshake always does a full key exchange (no such thing as a Session
* The handshake uses the Tor Project's ntor handshake with public keys
obfuscated via the Elligator 2 mapping.
* The link layer encryption uses NaCl secret boxes (Poly1305/XSalsa20).
As an added bonus, obfs4proxy also supports acting as an obfs2/3 client and
bridge to ease the transition to the new protocol.