SSH - A Secure Terminal and File Transfer Tool

The ability to access one machine from another has been a desirable feature for nearly as long as there were computer networks. Programmers developing code on slower machines would want the ability to log into and run their software on faster machines; faculty in one university might want to collaborate with research on a different universities cpmputers, ..., the list is endless. Originally, the ability to log into a machine remotely from another computer was provided by two pieces of software: telnet which allowed a programmer to log in and work on another machine (as if they were a user sitting at a terminal of that machine), and ftp (for file transfer protocol) which allowed a user to log into another machine and pass files between the local and remote machines.

While telnet and ftp provide terminal access and file transfer capabilities to a remote machine, their transmissions are completely exposed to being 'eavesdropped'. Any information, especially passwords, can be grabbed during transmission.

The spftware ssh/sftp (Secure shell/secure file transfer) were developed as secure replacements for telnet/ftp.

Obtaining an ssh Implementation

There are several implementations of ssh available for both Windows and Unix: if you are on a Mac or Unix system, there is an ssh client already built into the system. Open your Terminal application, and at the command line, type ssh, and you will be connected to the server and prompted for a password, after which you will be on the command line..

Using ssh

Assuming you've downloaded and installed the software from SSH Communications Security, here is how to connect to the machine.

Click on the ssh icon installed on your desktop. A blank, inactive terminal screen will appear. Click the Quick Connect on the tool bar, and then fill in the host name (in the image I am connecting to and the user name (weiss in the image-- you should use your own username that you received from me via email -- leave the other two boxes unchanged and click Connect:

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You will be prompted for your password and then connected to the remote machine. A pop-up may appear asking if you wish to name this profile (so you don't have to enter the information next time).

Once connected you have a nice terminal interface. Copying and pasting using your mouse is available (though you use Ctl-Ins and Shift-Ins for copy and paste respectively (rather than the Ctl-C/Ctl-V you're probably accustomed to).

You can open additional terminal windows by going to Window/New Terminal on the menu.

ssh also provides a GUI-based file transfer facilitiy. Go to Window/New File Transfer — you can access this facilitiy either via the other icon (the one that looks like a folder ) or by clicking the same icon on the tool bar of the ssh window.

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You can drag and drop files between your local PC and the remote machine.

If you are on a Mac, there is a command, sftp, that provides for file transfer between your local machine and a remote host. It is invoked the same way as ssh (username@hostname), and then takes you into a command line environment where you can list directories (locally and remotely), change directories (again at both ends), and upload (local-to-remote) files (the 'put' command) and download (remote-to-local) files (the 'get' command).