Synergy war story

[Giles Orr]

Not really a war story - this was just a minor skirmish.  May be of use to
Synergy users.  Includes an encryption question at the end.

I have two machines sitting side-by-side, one running Ubuntu Precise, the
other running Debian Jessie.  I decided to connect the displays with
Synergy (despite the problems I'm about to detail, it's a fantastic piece
of software if you're not aware of it, allows keyboard and mouse sharing
between almost any set of OSes you can name).

Having set up ~/.synergy.conf I ran:

   $ synergys -f

on the machine whose mouse and keyboard I wanted to use.  Then on the
client machine I ran:

   $ ssh -f -N -L 24800:desktop:24800 desktop
   $ synergyc -f localhost

at which point I got a message on that side: "WARNING: failed to connect to
server: incompatible client 1.3".  Further research revealed several
interesting details: Debian has synergy 1.4.12. Ubuntu Precise has synergy
1.3.8 installed, and nothing newer is available (someone has put 1.4.x in a
PPA, but I didn't want to go that route).  Synergy 1.4.x appears to finally
include encryption (after using it for six years I can finally stop using
that mind-bending backwards ssh connection?!).  So great, I go to synergy's
own website and get a .deb file of version 1.4.15 and install it.  First
problem: they built it without man pages.  So I used the man page included
with the Debian version, and work out that I wanted to run "synergys -f
--crypto-mode gcm --crypto-pass passwd" ... to which it responds
"Unrecognized option: --crypto-mode".  So there's the second problem: they
built it without encryption.

There appears to be a way to get Debian packages for Ubuntu.  I haven't
bothered: I don't love the ssh method, but it works and I know it's secure,
so I'll keep using that.

This brings me to my question: Debian's synergys man page details four
modes of encryption:

   ofb Output feedback mode.
   cfb Cipher feedback mode.
   ctr Counter mode.
   gcm Galois/Counter mode.

I know almost nothing about cryptography, but a cursory glance at Wikipedia
suggested to me that gcm was the best choice, and that ssh was considerably
better?  Am I totally off track?  Thoughts and recommendations appreciated.

-- 
Giles
http://www.gilesorr.com/
gilesorr-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org
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