Disable Screen Sharing’s lack-of-encryption warning

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I use OS X’s Screen Sharing quite often around the house, and not just for Mac-to-Mac connections. It turns out that screen sharing also works well for talking to Unix machines, of which I have one (running Ubuntu). However, when you connect to a Unix box using Screen Sharing, you see an annoying warning dialog that states:

The computer “” is running a VNC server that does not support Screen Sharing keystroke encryption. Text you type to this computer may be intercepted over the network. Do you want to continue connecting anyway?

If I were connecting to this machine from outside the home, on a public network, the lack of encryption would definitely be an issue. However, I’m not—I’m connecting to it on my local network, inside my firewall, so none of the data is transmitted externally. As such, the warning is more of a nuisance than anything, because it must be dismissed each time I connect to the Unix box. Or, I should say, it used to require dismissal, but no longer.

Thanks to a hidden preference setting, it’s possible to disable this warning. Quit Screen Sharing if it’s running, then open Terminal (in Applications -> Utilities) and enter this command:

defaults write com.apple.ScreenSharing dontWarnOnVNCEncryption -bool TRUE

Press Return at the end of the line, and that’s the end of the warning box—future connections to unencrypted hosts will happen automatically, without the need to first dismiss the warning dialog. If you’d ever like the warning back, quit Screen Sharing, open Terminal, and repeat the command, but change TRUE to FALSE.

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