HKExSh TODO Ideas
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Chaff Improvements
- Zipf or other distributions for chaff freq, packetsz
- Mimicry of hand-typed traffic for chaff on interactive sessions
- Client-input chaff file data (ie., Moby Dick)

KEx: Look at ECIES: https://godoc.org/github.com/bitherhq/go-bither/crypto/ecies

Architecture
(DONE) - Move hkexnet components other than key exchange into a proper hkex package
  (ie., hkexsh imports hkex) - hkex should be usable for other client/svr utils,
  ala 'hkex-netcat')
  (parts split out into hkexnet/*, hkexsession.go)
- Make KEx fully-pluggable: isolate all code to do with Herradura into a
  KEx-neutral pkg so it can be swapped out for other methods (eg., DH etc.)

Features
(DONE) - Support for hkcp (hkex-cp) - secure file copy protocol
(DONE) auth tokens to allow scripted hkexsh/hkexcp use
- hktun - tunnelling - multiple tunnel sessions co-existing w/shell sessions

Alternate transports for hkexsh.Conn - HTTP-mimicking traffic, ICMP, ... ?
(Whatever golang can support for net.Dial(), net.Accept(), io.Reader/Writer
 should in principle be usable as substrate for hkex.Conn)
- hekxsh-over-ssh