understanding ssh

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To: secureshell@securityfocus.com
Date: Sat, 10 Jan 2004 20:31:04 +0100

Hello!

I try to understand what happens using ssh.

But I´m not sure at all and hope anyone can help me.

My problems belong to the transport-layer:

Starting a ssh session, the client and server handle out which public key
authentication is to use (RSA/DES).
After that, the server sends in this example the DES public key.
The client compares this key with the key saved in file "known_hosts".
If the entry matches, client and server handle out which symmetric
algorithm should be used for encrypting data.
After that, ssh uses diffie-hellman to create a key for encrypting data
with 3DES.
Now, the sending data will be encrypted with 3DES.

Authentication can start now.

Is that correct?

I read something about randomised sessions. What is the meaning of
this? Does it belongs to creating keys with DH?
What about the sessions to differ between ssh connections?

And what about the session integrity provided through sha1 or md5 hash
algorithms? Where do I find the md5 checksum? When will it happen?

What about ssh1, does it only use RSA keys? Are they created like DES
when installing ssh or when creating a ssh session.

Does the symmetric key change after one hour?

Thanks a lot for your help!!!!

Greetings,

Sven

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