Synergy 1.7.3


I’d like to announce the release of Synergy 1.7.3.

» Download Synergy v1.7.3-stable

This version fixes the major SSL bugs (see below for details). Version 1.7.4 is due in about a month (track our progress).

Here’s the bug fixes:

  • Bug #4565 – Incorrect plugin downloads on Debian and Mint
  • Bug #4677 – Windows service log file grows to very large size
  • Bug #4651 – High logging rate causes Windows service to crash
  • Bug #4650 – SSL error log message repeats excessively and freezes cursor
  • Bug #4624 – Runaway logging causes GUI to freeze
  • Bug #4617 – Windows service stops after ‘ssl handshake failure’ error
  • Bug #4601 – Large clipboard data with SSL causes ‘protocol is shutdown’ error
  • Bug #4593 – Locking Windows server causes SSL_ERROR_SSL to repeat
  • Bug #4577 – Memory leak in GUI on Windows caused by logging
  • Bug #4538 – Windows service crashes intermittently with no error
  • Bug #4341 – GUI freezes on first load when reading log
  • Bug #4566 – Client or server crashes with ‘ssl handshake failure’ error
  • Bug #4706 – Installer is not output to build config dir on Windows
  • Bug #4704 – Plugin ‘ns’ release build is replaced with debug build on Linux
  • Bug #4703 – Plugins are not built to config directory on Mac
  • Bug #4697 – Timing can allow an SSL socket to be used after cleanup call

And we also made some improvements:


Synergy 1.7.2

I’m excited to announce the release of Synergy 1.7.2!

» Download Synergy v1.7.2-stable

Here’s the bug fixes:

  • Bug #4564 – Modifier keys often stuck down on Mac client
  • Bug #4581 – Starting GUI on Mac crashes instantly on syntool segfault
  • Bug #4520 – Laggy or sluggish cursor (ping spikes) on Mac when using WiFi
  • Bug #4607 – GUI doesn’t start after install on Windows

And we also made some improvements:


Synergy Basic vs Pro

Some people ask us “What’s the difference between Synergy Basic and Synergy Pro?”

The following comparison matrix shows the differences, and also includes some info about Synergy Enterprise, the next tier up…

Upgrade to Synergy Pro

We established the need for a Pro version to accommodate our users in business, education and government.

In these environments, security is one of the most important aspects, since millions of dollars can be at stake over even the smallest piece of information, such as a password. Users in these environments also can’t afford to spend the time figuring out solutions when things go wrong, so we provide a way to get help when needed.

Read more about SSL encryption: SSL Encryption in Synergy 1.7

If you’re interested in Synergy Pro, please purchase from our website ( or contact our sales team (

SSL Encryption in Synergy 1.7

SSL encryption is now available in Synergy 1.7!

Introducing SSL encryption for Synergy. Most companies rely on tall walls surrounding their networks for security, leaving their internal network vulnerable. The most effective method of protecting sensitive data is for point-to-point connections to be encrypted, even when on an internal network.

The SSL encryption feature in Synergy provides this point-to-point security, and will protect your setup against malicious users detecting highly sensitive keystrokes (like passwords).

Here’s what unencrypted Synergy network traffic looks like to a malicious user after performing a MITM attack on your network connection. The “p” key is visible in plain sight, same goes for “a”, “s” (you get the idea).

A Wireshark screenshot showing Synergy's unencrypted network traffic.
A Wireshark screenshot showing Synergy’s network traffic when unencrypted (the “p” key is highlighted).

How high is the risk of this attack?

MITM attacks constantly go undetected (according to the Verizon 2011 Data Breach Investigations Report). When an attacker sniffs your internal network traffic, they may use a packet inspection tool (like Wireshark, a freely available tool) to analyze data sent between your computers. ARP spoofing is a popular technique used to perform MITM attacks on wired networks.

How does Synergy prevent the attack?

Synergy uses certificate based asymmetric encryption called SSL (Secure Sockets Layer), the de facto implementation of TLS (Transport Layer Security).

With SSL encryption, here’s what traffic looks like to a malicious user (see below). The message is completely unrecognizable when viewed with a packet inspection tool – you can’t tell if its a key press, a mouse movement, or anything else.

A Wireshark screenshot showing Synergy's OpenSSL encrypted traffic.
A Wireshark screenshot showing Synergy’s secure SSL encrypted traffic.

What about symmetric key encryption?

Security experts at Defuse Security (security research and development) demonstrated that a roll your own symmetric key encryption is a bad idea, and demonstrated how it could be easily exploited. This type of encryption is no longer used in Synergy and has been completely replaced by SSL.

How do I upgrade to SSL encryption?

This feature is available in Synergy Pro, a version of Synergy designed especially for use by professional users (such as business, education or government). Existing customers who purchased before the introduction of Synergy Pro are given a complementary upgrade. If you’re new to Synergy, you’ll need to purchase Synergy Pro from our website.

We hope you enjoy the peace of mind that this feature brings. As always, please let us know if you have any feedback or comments (you can email us or leave a comment below).

Synergy 1.6.3

Synergy 1.6.3 is now available to download.

Bug #4349 – Mouse click does not always bring window to front
Bug #4463 – Unidentified developer error on Mac OS X
Bug #4464 – Code signing verify failure not reported on Mac build
Bug #4465 – Binary (syntool) is not code signed on Windows
Enhancement #4455 – Replace version with branch name in package filename

Download Synergy for free!


Good news…

Download Synergy for free (as in free beer).

Free Beer

I decided to create a free download page for Synergy, which makes older versions of our compiled binaries and source code available without the need to pay (for the latest version, users still need to purchase).

I’m hoping this will make Synergy more accessible to people who can’t afford to pay (for example, students or those living in developing countries) while still keeping our project funded. I am trying to figure out how to give the latest version to those who genuinely cannot afford it, as I believe this is important, but haven’t yet figured out a way to make sure this won’t be abused (but I’m working on it).

Secondly, while Synergy is free (as in freedom) many free download sites host our compiled binaries in order to profit their own business without giving back to the Synergy community. While this is legal and permitted by the GPL (how we license our work), I feel it goes against the spirit of our community. Given that file hosting is so cheap these days, I don’t feel that just providing hosting is enough. Free download sites profit from the work of others by either advertising (which is surprisingly lucrative) or bundling the original version with other (unwanted) software which results in a poor user experience. In an ideal world, companies profiting from our work would contribute back to our community, but this doesn’t appear to be happening, and I’m pretty sure it never will (there are countless ways to contribute, and file hosting just doesn’t cut it for me).

Please link to the free Synergy download page from your website or blog to make our advert-free download page the first result when searching for “Synergy free download” on search engines.

<a href="">Download Synergy for free</a>


Synergy 1.6 is here!


I’m absolutely thrilled to announce that Synergy 1.6 is now stable and ready to use!

Download Synergy 1.6

We’ve been working on version 1.6 (which introduces the auto config feature) for around 6 months now, and its finally ready. Thank you so much to all who tested and contributed to our 1.6 beta version, we really appreciate all your hard work and support.

Auto config (new feature)
Look ma, no hands!
Xinyu Hou (a Software Engineer here at Synergy) has been working tirelessly on the new auto config feature for quite some time now, and it’s finally stable and ready for everyone to use. No more awkwardly hand-typing IP addresses and screen names for you guys! Just download and install Synergy, then watch it go…

Shift key bug fix (Windows)
Microsoft released several security fixes over the last 3 months, which caused Synergy users to experience issue #4055 (shift key stopped working completely on clients with Windows server). Thanks to Chris Ribe (one of our valued contributors), this issue has now been fixed! A round of applause for this guy, please!

Bonjour is now optional
Our beta testers gave us some very useful feedback about the Bonjour installer: apparently its not always welcome, so we made it optional. You’ll still need Bonjour for auto-config to work, but we added an automatic download feature within the user interface, so you only need to authorize the install when prompted.

Drag and drop on by default
Previously, you needed to enter your premium password to use the drag and drop feature (available on Windows and Mac). We have since enabled drag and drop by default for everyone (no need to login anymore).

Make $5 by referring a friend!
We’ve just added a referral reward program for Synergy. When your friend buys Synergy, we give you $5, just for spreading the word. It’ll be the easiest $5 you ever make, plus you’ll be helping the development of open source software. There is no limit to how many friends you can refer, and no limit on how much you can make. Go to your Synergy account to refer a friend today!

Mac OS X Yosemite
Synergy is now fully supported on Mac OS X Yosemite 10.10. Apple had changed their binary signing policy, which caused the Synergy app to be rejected by Gatekeeper. This has now been fixed, and Synergy is now officially supported on Yosemite.

Better at Windows UAC
When switching between the login screen and the normal desktop, Synergy now elevates the process automatically for you, depending on whether or not its needed. For now you may still need to elevate Synergy manually to use elevated programs, so we made the manual elevation option available in the settings menu.

Even more bug fixes!
Please check out our ChangeLog for a full list of bugs fixed in 1.6 (this includes beta and stable versions).