$ sudo apt-get update
$ sudo apt-get install libssh-4 

libssh-4 is installed in your system.

Make ensure the libssh-4 package were installed using the commands given below,

$ sudo dpkg-query -l | grep libssh-4 *

You will get with libssh-4 package name, version, architecture and description in a table

libssh-4 package basic information: