Timing Analysis of Keystrokes and Timing Attacks on SSH – Watching the timing between keystrokes sent over SSH and other encrypted protocols, some information can be obtained about the contents of the packet.
You can download it from the following link: https://packetstormsecurity.com/files/download/25257/ssh-timing.pdf
Source: https://packetstormsecurity.com/files/25257/ssh-timing.pdf.html