Skip to main content

Encryption and fingerprints in Synergy 1

Updated

Written for Synergy 1 (v1.21.4), checked 3 October 2026.

Synergy 1 encrypts the connection between your computers with TLS when Enable TLS Encryption is ticked. It's on by default and needs a Synergy 1 Pro or Business license; with a Basic license, Synergy 1 turns it off when it starts.

Turn encryption on

  1. On each computer, open Edit > Preferences (on macOS, Preferences is in the Synergy menu) and go to the Network tab.
  2. Tick Enable TLS Encryption and click Save.

Do this on every computer. The padlock in the status bar shows Encryption Enabled when you hover over it once the computers are connected.

Trust another computer the first time it connects

The first time a client connects to a server, Synergy 1 asks you to check that each is talking to the right computer:

  • On the client, Connecting to a new server asks Do you want to connect to the server?
  • On the server, when Require client certificates is ticked, New client connecting asks Trust client and allow connection?

Both windows show the Server Fingerprint and the Client Fingerprint side by side. Compare them with the other computer's own fingerprint before you click Yes: on that computer, click the fingerprint button in the status bar (View local fingerprint) to open Local Fingerprints. Click Show hash in either window to compare the fingerprint as text rather than as a picture. Only click Yes if they match. Clicking No on a client stops it connecting.

Once you've clicked Yes, Synergy 1 remembers the other computer and doesn't ask again, unless that computer gets a new certificate: after Regenerate certificate, a reinstall that removed its settings, or Help > Clear settings. Then compare the new fingerprints the same way.

Encryption settings

All on the Network tab of Preferences:

Setting What it does Default
Certificate The certificate file this computer uses. Synergy 1 creates one for you. synergy.pem in the tls folder
Key length 2048 or 4096 bits. A longer key is stronger. 2048
Regenerate certificate Makes a new certificate. Every other computer will then ask you to trust this one again.
Require client certificates Server only: the server asks you to trust each new client before it can connect. Unavailable on a client. On

Forget a trusted computer

Quit Synergy 1, then delete trusted-servers (on a client) or trusted-clients (on a server) from the tls folder. Synergy 1 asks you to trust each computer again on the next connection. Where the tls folder is:

  • Windows: C:\ProgramData\Synergy\tls
  • macOS: ~/Library/Synergy/tls, or /Library/Synergy/tls when settings are kept for all users
  • Linux: ~/.config/Synergy/tls, or /etc/Synergy/tls when settings are kept for all users

For security teams, the wider picture: Business & Enterprise Hardening Guide