HET Help on SSH

What is it?

SSH is a secure (i.e., encrypted) method of accessing a computer over the Internet. Just like telnet or rlogin/rsh it allows you to open a shell on the remote computer and, like FTP, it allows you to tranfer files over secure lines.

Why do I need it?

Basically, because this is the only way of accessing the HET cluster from the outside world! =;-) In order to do so, you should type (assuming that you are luser@het.brown.edu): ssh luser@now.het.brown.edu. To find out more "tricks", take a look at the Newbie Help Page.

What is the problem with `telnet/rlogin` and `FTP`?

In one line: "You password is sent, over the Internet, as clear text!" Thus, anyone snooping the network can read it.

Where do I get it?

MS Windows(R):
- For opening a Shell: Use PuTTY;
- For File Transfer: Use WinSCP.
*nix: It should already be installed on your computer. If it is not, ask your SysAdmin to do so.
- To open a Shell:
```
ssh luser@now.het.brown.edu
```
- To put (from outside to HET) a file:
```
scp file luser@now.het.brown.edu:
```
  (note the ":" at the end of the command!)
- To get (from HET to outside) a file:
```
scp luser@now.het.brown.edu:file .
```
  (note the "." at the end of the command!)
- Alternatively, for file transfers you can use:
```
sftp luser@now.het.brown.edu
```
  and, then, use the standard FTP commands (get, put, bin, prompt, hash, mget, mput, ...)

Will I have to type all that every time?

Not really, you can create an alias in your shell:

BASH: alias now='ssh luser@now.het.brown.edu'
TCSH: alias now 'ssh luser@now.het.brown.edu'

And, for file transfers, you can either use the sftp utility or more recent versions of some GUI program, like GFTP.

When I try to connect...

The very first time that you try to connect, your computer has no means of knowing that that it is really talking to now and not with some intruder that is listening in the line. Thus, now is going to send a key to your computer, that will look like:

---- BEGIN SSH2 PUBLIC KEY ----
Subject: root
Comment: "DSA hostkey"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---- END SSH2 PUBLIC KEY ----

There is, also, something called the fingerprint of a key. For now, the fingerprint is:

xunil-pucuk-cybur-kogut-kusur-titor-gocol-degem-cihyc-rylyz-ryxyx

After that, whenever you connect to now your computer will check the key, to see if it still matches. If it does, all is fine and you login with no problems. Otherwise, your computer will make a big fuss about it and will ask you if you really want to continue. In most cases, the only thing you will see - if it happens - is the fingerprint for the "corrupted" key. In this case, either someone cracked into now and changed the keys, or some SysAdmin changed the keys (either on purpose/knowingly or not). If that happens, email admin@het in order to let us know. If you decide to continue, your password may be compromised.

If you have any further questions, let us know: admin@het.

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zeus at olympus dot het dot brown dot edu

Last modified: Wed Feb 4 11:57:43 EST 2004