OpenSSH 9.5: ObscureKeystrokeTiming no

To start with I am a big fan of OpenSSH; however in OpenSSH 9.5, the default behavior was changed to obscure keystroke timing by adding random delays to data being sent. As it is currently implemented, for the vast majority of people, it will cause a significant degradation in performance while not providing any meaningful additional security. Furthermore, if you are not aware of the new ObscureKeystrokeTiming option, debugging these problems is difficult because of the random nature of the change in OpenSSH and the fact that the problem could be in either computer or in the network itself.

The main symptoms I see are very slow start times and slow screen resizing. This caused a lot of frustration for my work flow because I pop up many emacs windows to compare file differences. Another symptom I see is that emacs hangs whenever I attempt to resize the text selection usually taking about 30 seconds before it becomes responsive again.

So if X11 forwarding broke for you after a recent upgrade, try adding the following to your ~/.ssh/config file:

    Host *
      ObscureKeystrokeTiming no