Question about ssh_host_dsa_key

[Smoot Carl-Mitchell]

On Mon, 2008-06-09 at 14:10 -0500, Robert Dailey wrote:
> Hi,
> 
> I'm very new to Ubuntu Server and I'm just wondering what the key
> named "ssh_host_dsa_key" is for? This is located in /etc/ssh. Also
> another confusing concept is ssh-keygen. What's the point of creating
> public/private keys? Is this so I never need to specify an explicit
> password when logging into my ubuntu server via PuTTY on windows? I'm
> trying to understand how SSH works in Ubuntu so I can debug an issue
> I'm having with svn over ssh.

The host keys are the unique per host key.  When you connect to a host
for the first time, SSH will ask you if you want to store the host's
public key in your known_hosts file in the .ssh directory.  This is a
way to warn you if the connection is being spoofed by someone
intercepting packets or redirecting your connection to a different
server.  Paranoid sysadmins can require the public host key be passed
"out of band" e.g. manually installed on each client and set SSH to
disallow a connection unless the host is known.

The ssh-keygen program is used to generate public/private keypairs which
can then be used for passwordless authentication. If you generate a
keypair like this:

ssh-keygen 

The private key will be put in .ssh/id_rsa and the public key
in .ssj/id_rsa.pub.  You can generate a dsa key by running:

ssh-keygen -d

If you then put the public key on one of your servers in the
file .ssh/authorized_keys, you can then login without using a password.

Here is an Ubuntu HOWTO:

http://help.ubuntu.com/community/SSHHowto

-- 
Smoot Carl-Mitchell
System/Network Architect
smoot at tic.com
+1 480 922 7313
cell: +1 602 421 9005